I am sure a dedicated pre and 2 Ch Amp (plenty of choices) would improve sonic presentation from the RM40s. HOwever, before that I hop your RM40 has mid-panel upgrade and you have taken time to fine-tune RM40s (bass by removing/adding mass/putty, hi/mids tweaking using pots back of speakers)?..
Do call Brian-he will offer solid advice :)
Oh yeah RM40s are very revealing-once I started using them I had to discard couple of poor CD recordings! ... :)
Cheers,
Kishore