[size=10pt]Hi,[/size]
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[size=10pt]I am finalizing on what I may need to have a decent rig for approximately $1-1.5k. So far, I figure I want a decent soundcard, which in my opinion tends to be the ESI Juli@. As far as a DAC, I'm looking at either the Emotiva XDA-2, the TEAC UD-H01, or the Schitt Bifrost. I'm pretty dead set on the Bottlehead Crack Amp with the Speedball upgrade, as I think this is definitely the best value as far as Headphone Amps go.[/size]
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[size=10pt]My question is, in order to properly drive my HD650s, is there a part of the equation I am missing? Is there something that I am planning on getting that I don't need? For instance, I know that the Emotiva XDA-2 is classified as a DAC, a preAmp, as well as a Headphone Amp, which I have read does not do a great job of driving the more demanding headphones. I have also seen the TEAC UD-H01 categorised as a Soundcard, a DAC, and an Amp. Do I need to get an internal soundcard like the Juli@? [/size]
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[size=10pt]My computer has the P8Z77-V Motherboard which has an S/PDIF output, which I could essentially use as the signal input for the DAC, which would mean that I don't need to upgrade to the ESI Juli@. I'm trying to keep away from getting the digital signal from the USB port on my PC.[/size]
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[size=10pt]I am really in desperate need of some help regarding this since I would really like to get the most out of my HD650s, and I just want to get components that I can hold on to in the future, as I go deeper into this voyage of sonic discovery.[/size]
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[size=10pt]Thank you all for your help. I am very open to suggestion, and I appreciate your understanding the fact that I am very new to this.[/size]

Changed my mind, and went for the TEAC UDH01. After reading up on some positive reviews and realizing that the UDH01 has better volume control; a dial as opposed to the button input on the Emotiva XDA-2, I placed the order for the UDH01. Planning on running the DAC via the S/PDIF out from my motherboard for a while, and then getting the Crack OTL w/ Speedball next month.
 
Once I have those two, I think I should have a pretty decent setup, or so I think, because who knows what happens in a month.

Why is this so difficult? After I ordered the UD-H01, I found a review of the UD-H01 against the Onkyo A-5VL Integrated Stereo Amplifier. Upon further research, and some reading, I found out that the A-5VL outperforms the UD-H01 not only in that the A-5VL has a better soundstage, but also that it is a pretty good dedicated amp for bookshelf speakers.
 
Futhermore, upon reading about the A-5VL, and seeing that the A-5VL is currently selling for approximately the same price as the UD-H01, I ordered it. All was great until I found another reviewer stating that the Onkyo A 9555 Amp is even better than the A-5VL. 
 
Whichever I do end up with, there is the one fact that cannot be overlooked: this will be my FIRST DAC/Headphone Amp for my HD650.
 
Now if only someone would put in their two cents so that I can at least figure out what to get. I don't want something that is the top of the line, but would love to keep within $400-600 range. 

Crack is a great amp, but for the 650s I'd prefer something solid state. They are warm enough as it is and something that will tightly control bass reproduction would help them max out their abilities.
I much preferred them with agd nfb-5 than with the crack.
 
Would you care to expand on what you have against the USB? S/PDIF has it's pitfalls too and you may end up spending more to get it right.
 
Regarding the DAC selection - this is the part of the chain that will make the least impact on your experience, so stop worrying about getting the best one (there's no such thing). Reviews are a great way of getting the taste of the experience, but when it comes to conclusions and preferences take them with a grain of salt.
 
Unless you care about surround sound processing capabilities (games/movies), you may not need a soundcard. On the other hand if you do get one, then the external DAC may be an overkill. Do it all step by step and hopefully you'll reach satisfaction level before your wallet gets anorexia.

PleasantSounds,
 
Thank you so much for your response.
 
First off, I received the TEAC UD-H01 today. Setup was quite easy, as all that I really had to do was download the driver for the DAC, connect the power cable, and connect the UD-H01 to my PC via... USB. 
 
First off, I played music at 192kbps quality. The improvement in detail was quite noticeable, however, the range of sound available seemed to not be as wide as what I expected. The frequencies at either ends of the spectrum seemed to drop off. That being said, the sound that was there, was quite detailed. There was an immediate "accuracy", for lack of a more accurate word, present. Instruments started to sound more like how they do in real life, and I am still amazed at how much I really have been missing out on. 
 
Before, the different instruments sounded like they were muddled together. There was no defined beginning or end to the different instruments. The defined sources of the sounds were also quite unrefined. 
 
Now?! Well, how do I go about this? 
 
I have owned my HD650 for over 6 years, and I have just now begun to understand just what I may have possibly invested in all those years ago. 
 
Switching over to 256kbps, the sound may have improved, and perhaps listening to it over and over, then switching back to 192kbps, I may hear real difference. I am sure it's there. 
 
There is a long story about why I didn't have a PC for the last 5 years, but prior to my last PC malfunctioning, I had ripped approximately fifty albums from .wav to .flac. Since I switched hard drives into my new PC, I downloaded the extension for Windows Media Player to be able to play FLAC files. Moments later, and I must say that I am now corrupt with this most extraordinary experience. What seems to be every detail to the sound is present in the most intricate display of instruments and vocals. They sound as if I am sitting in the front row of a very intimate concert. The sound stage could be just a bit wider, but is the most accurate I have ever experienced through any headphones. 
 
Every instrument seems to be there in its entirety. No more clashing of "like" frequencies. Every piece of the music is dissected, yet presented in the way that it is fused together with only the slightest thread of composition. Together, the notes of music enter the ears without any particular authority, in that they don't force me to accept them how I have been, rather, it seems more of a rescue. A truly blissful rescue!
 
The UD-H01 seems to drive the HD650 well enough, however, I'm not very satisfied with the weak bass with the .mp3 files. I believe all it took for me to become jaded was to hear my first .flac track through the UD-H01. It's going to be extremely difficult to not listen to the HD650 without a DAC now. 
 
The Onkyo A5VL shows up on Monday, and I believe once I receive it, I will send the UD-H01 back as I know that compared to the UD-H01, the A5VL is a better unit. I have also ordered the Audio-GD NFB-5.2, and will try it out. 
 
As far as my reservations about using USB as an input, there are times when there are a lot of issues with syncing, from what I can guess. What I am talking about is when I go from one folder to another to play a track directly from my hard drive, I sometimes hear scratching noises, or clicking. It's definitely not prevalent/consistent, but intermittently comes about. I plan on going out and getting an S/PDIF cable so I can compare if there is a change. 
 
Once again, thank you for your input, and I am very much looking forward to what is coming my way in the next few weeks, as I decide on what I ultimately want to use. Looking forward to hearing the cymbal reverberations, and the guitar strings vibrating on the pick for that fraction of a second.
 
Cheers! 

Any impressions on the A5VL yet? Interested in seeing your impressions on it versus the TEAC.
 
Also, sweet username, you drive an FD RX7?