What low-impedance headphones do you guys find that scale really well when plugged into an amp. I've tried the M50's through a receiver headphone out and through my Pa2v2 and I found that the Pa2v2, to my ears, tightened up the bass a bit and gave them just a tad more depth. So it seems that I've gotten a maybe 5 or so percent increase in sound quality. This is merely through my listening though and not the general knowledge. What do you guys think?