Most of the time moving from a receiver to an amp won't be lateral if you listen at higher levels. Normally at lower levels receivers have no problem pushing speakers, its only when you really crank it that a receiver might struggle.
If you are looking for a great 2 channel amp and don't want to spend an arm and a leg look into emotiva. Their two channel amp got a great review on this site. You can see it
here.
If you want real improvements at any level look into treating your room as that is a huge factor in sound. I.E. Much larger improvement for the money.