One of my most accomplished audio buddies is a fan of NAIM amps and preamp. He pairs them with Focal Electra 906, and prefers the NAIM over some very good Cary tube gear.
The most important thing is that you like the sound. It's hard to say where the issue is for you, but it's always very personal, and of course interactive with the rest of a given system. It might help if you could give some hints as to whether it's too bright, or too dull, lacking bass, booming bass, etc. Have you tried adjusting the speaker placement a bit to increase or decrease bass reinforcement, and toe in? I fine tuned my system with things like cables, power supply upgrades, placement, etc., and other stuff that's supposed to be barely audible, but yet it's made the difference between being good and spectacular with pretty much the same gear.