I doubt you'll find a better amp than your RM9. Have you tried Roger's RAM KT88s ($65 each)? You might feel like you have a new amp for less, and that RM9 is a classic (but it does not sound like you are actually thinking of selling it). If you really have the itch, I would try a used Quicksilver V4 Monoblocks. Sound great, american-made, point-to-point very reliable, and very easy to bias - of course that's true of your RM9 as well (except the point-to-point).