SS Pre Recommendation

Usually bass problems have little to do with Preamps in general, or it is unlikely that a Preamp would cause boomy bass. Typically boomy bass is the result of speaker and room interaction.

Nevertheless, in response to your question about SS preamps, you could take a look at those from Pass Labs. Even the older L or P were excellent. Although personally I do like the ModWright SWL9.0SE, which although is tubed, sounds very neutral and more like a good SS preamp, than a tubed one.

I agree with Cmk about the boomy bass.

Having said that, look at Klyne for SS preamps.

Shindo, Krell

That is definitely correct on bass. In terms of preamp, many do well with wavacs. I like particularly the Lyra Connoisseur and surprisingly the Krell Two. Obviously, the even better idea would be to consider the wavac pre.