recommend full featured preamps?

Lloydc,

What are the speakers in your system?

Often, the problem you describe with bass at low levels can be due to a mismatch between amp and speakers, especially with tube amps and lower efficiency speakers that have a more complex load to handle.

For example, I'd love to have your amplification but I have yet to discover a tube amp that could drive my fussy Ohm 5's properly (believe me, I'm still looking but am not hopeful).

I replaced a 360w/ch SS Carver m4.0t with a 100 w/ch Musical Fidelity A3CR for exactly the same reason, poor bass at lower to moderate volumes. The Carver actually went louder and sounded great doing it.

If this is the case with you, then tone controls might help compensate but better matching of amp and speakers could correct the problem and negate the need. It did in my case. I don't think I've touched the tone controls on my Carver preamp since.

Have you considered 'tuning' your room?
I know what it is like to be space/layout constrained, but just maybe, a few small adjustments would help.
Something for first reflection....a dense wool tapestry like I use or some carpet directly in front of the speakers.
Extra points scored for good imagination here.

Just may help!

My speakers are Infinity Prelude PF-R, which are highly efficient - but I think their impedence curve does dip down to almost 3 ohms at one point. The Baron is not like other tube amps, its output is more dependent on the speakers' imp. curve., but seems to work ok (it is very adjustable). The Preludes do have switches for adjusting the bass output, but they just make it boomy - the wrong curve for my needs, I guess. I do have a rug in front of the speakers, but more work on early reflections is probably a good idea. TV monitor is between them, unfortunately, but speakers are forward enough to avoid 1st reflections from tv's edges. Thanks to everyone for all the thought and suggestions.

"I think their impedence curve does dip down to almost 3 ohms at one point."

That's probably a red flag with most any tube amp.

What is the amps rated output in 8, 4 and 2 ohms? If it does not double each time or come close, that could well account for the poor bass response.