Ev's advice is sound (no pun intended). Go for what sounds good to your ears more than anything else. If you think it sounds good, why worry about abstract math?
That said... I got my amp in last night (because change is good) and the change with the Q701 is noticeable. (I too was running off the Sound Blaster Omni.) It's really true that you don't know what they're capable of until you amp them. They didn't sound bad before, but they sound really good now!
My point? If you're satified now, don't bother. If you want to upgrade because you're feeling the itch, an amp will definitely serve you well. I'm sure any of the inexpensive ones in the guide will be fine (E12, Magni/Vali, E09K, O2).
Dude, I've learned to be really careful of that quote. It's almost always true, and not always for the better. For example, when I finally dropped some real cash on a nice suspension for my motorcycle, it was night and day. I had no idea what I was missing and I could never go back. Now I HAVE to spend money for a nice suspension on every bike because I hate the feel of a crappy suspension. It's expensive!
If you're satisfied with your current sound, be careful about upgrading or you may never want to go back! lol
Itchy, must scratch itch! lol
I get the impression that head-fi is a gathering place for itchy people.