I picked up a pair of used Paradigm Atoms for ~$80, and they seemed pretty decent. Noticeable mid-bass bump (much more so than M3) but overall sound was good.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8