Sounds like you're running something similar to Joe's JLTi tube-buffered gainclone. I found my gainclone works very well with my tube preamp too, although the bass is lacking at the very bottom end.

Here's a thought: a 4 channel gainclone for biamping purposes. Build the two HF channels a usual, but give the two LF channels about 20,000 uF of reservoir capacitance per channel. From what I've read, increasing power supply reservoir increases bass quality, but mids and HF suffers.

Gar.

• JLTi Tube Buffered Gainclone