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.

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.

I have an Ayre K5 and it is wonderful, put it in your short list before you buy.