recommend full featured preamps?

Best I could tell you is pick up a used Carver pre-amp. These can be had for not much, are very good and have lots of flexibility features if needed. Get one like the C-6 in my system that has separate pre-amp outputs voiced to sound more like a tube pre-amp than SS, if you have leanings towards tubes.

The addition of tone controls in your system will only compromise fidelity.

the accuphase line of pre-amps is one of the most intensive ive seen with bass, treble, balance (left and right), some models even have db gains. mono switch, loudness compensation switch as well as other nice goodies.
And they also sound great!

"The addition of tone controls in your system will only compromise fidelity."

I would agree with the audio purest perspective that use of tone controls are better avoided, if possible, but sometimes it isn't for whatever reason and the advantages of adjustable settings and options can far outweigh the disadvantages compared to the alternatives.

If pre-amp flexibility is critical to your application, a properly functioning second hand Carver pre can likely do the trick without breaking the bank.

Would need more details about your system and setup to suggest how you might avoid this, if possible.

another angle

http://www.proaudio.com/product_info.php?manufacturers_id=72&products_id=2198