Need guidance on DAC/headphone amp with aux input to PC

[glove_of_power]

I am looking to buy a a good-quality USB DAC which will also serve as a headphone amp for my main PC.  I will also be using it to digitize recordings from my reel to reel.

Must haves:
-front volume control for headphones
-RCA outputs to go to my Marantz stereo amp/speakers
-RCA aux input that goes to the PC, not just the internal amp
-good quality DAC capable of 24bit/96kHz
 
Other features which would be nice:
-quality analog to digital conversion for my reel to reel
-tube amp (ideally 1 tube so I could have fun swapping them for a lower cost)
-independent power supply (not powered over USB)
-no output transformer
-a second volume knob which controls the volume of the RCA outputs to the stereo (my old Tascam US-144 had this and it's a nice feature although it seems super rare)
 
the headphones it will be driving are AKG M220 and Grado Labs SR225s, so nothing with very high impedance.  Thank you for your advice!

 

[buke9]

I doubt you are going to find twin volume controls as you already have surmised . There are many that have variable control out of the rca's that acts just like a preamp or is one more the case. You need to state a budget to get more accurate submissions to what you can find.

 

[PurpleAngel]

  I am looking to buy a a good-quality USB DAC which will also serve as a headphone amp for my main PC.  I will also be using it to digitize recordings from my reel to reel.

Must haves:
-front volume control for headphones
-RCA outputs to go to my Marantz stereo amp/speakers
-RCA aux input that goes to the PC, not just the internal amp
-good quality DAC capable of 24bit/96kHz
 
Other features which would be nice:
-quality analog to digital conversion for my reel to reel
-tube amp (ideally 1 tube so I could have fun swapping them for a lower cost)
-independent power supply (not powered over USB)
-no output transformer
-a second volume knob which controls the volume of the RCA outputs to the stereo (my old Tascam US-144 had this and it's a nice feature although it seems super rare)
 
the headphones it will be driving are AKG M220 and Grado Labs SR225s, so nothing with very high impedance.  Thank you for your advice!

 
USB DAC do not come with analog inputs, guess what your looking for is an Audio Interface or external sound card.
Guessing an Audio Interface (with it's software) is more likely to have more of the features your looking for.
http://www.bhphotovideo.com/c/search?ipp=100&Ns=p_PRICE_2%7c0&ci=14834&setNs=p_PRICE_2%7c0&N=4294550051&srtclk=sort