So you came over here looking for ways to improve the sound of your system but after looking around a bit you find that it's kind of easy to become obsessed with this stuff. You're noticing that audiophilia is a disease, and a very expensive one. My advice is to set some ground rules for yourself and stick to them as long as you can. Here are mine:
1) Stick to 256k mp3s. These are the files you've already got. They can sound awesome. Resist the urge to even try some hidef. You will receive offers to try out hidef files for free. Ignore them.
2) Stick to $200 headphones. There are plenty of great $200 headphones. I want to try them all. That's another problem.
3) Since I use a Surface 2, I'm sticking to portable, USB powered DAC-Amps, also under $200. This is an interesting segment of the market with great new products arriving every 6 months. Possibly yet another problem.
I know it's tough to stick to these limits. About a week ago I became obsessed with getting some HD650s and a Bottlehead Crack. Fortunately, a quick look at my credit card balance brought me back from the edge.
Good luck and good (enough) listening.
You're not wrong to be honest.
1) I agree - 256k AAC VBR is, to my ears, effectively transparent - meaning that I cannot hear the difference between that and lossless - Although I do, as a matter of course, rip classical stuff to losless
2) Yep, I use Q701s, which can be found cheap these days, for home use, and the Senny HD-25 IIs as portables. Both can be had for around 200 - 300. With these two in my stable, I've come to realise that other, even more expensive, headphones sound different, but not necessarily better.
3) Again I agree. I use a FiiO E17 as a DAC amp combo almost exclusively with my Q701s, and I'm not left wanting. As for mobile use I find my iPod nano 7th Gen on it's own powers my HD 25s amazingly well.
I've had the opportunity to listen to some expensive gear over the last year, and to be honest, while I can appreciate the difference, it was just that - different, not better, not worse.
I'm in the fortunate position where I could go out today and simply buy the Senny HD 800 and HDVD800 amp dac for the best part of 4k without any money worries, but having heard them I would say that, for me at least, the difference between them and what I have now would in no way justify 4k.
You guys with your 200 buck DAC AMP and your 200 buck HPs basically have by far and away the best value for money in this game - you're 90% of the way there already. Going from 20 buck HPs to 200 buck HPs is a "woah", going from 200 buck HPs to 2000 buck headphones is more of an "oh" in comparison.
GAS is your greatest enemy in this hobby and it often gets you very little while at the same emptying your wallet of significant amounts.