cary slp98 pre with yba 600 power amp compatable?

I would make the choice based on sound quality, and not if the preamp is tube or SS. If not, the risk of making a mistake becomes much greater. Also, I'm not sure how you plan to go about this, but if you get something without demoing it first, you can't expect to be happy. Reviews and comments can only get you so far.

Speakers? I owned the SLP98P hot rod version from Upscale and liked it a lot with my SS Plinius amps and Dynaudio Speakers. 6SN7 based tube preamps have a lot of soul in my experience and are often a welcome addition to a SS system. Be careful turn thing off and on in the right order, though, or you may not like what happens to your gear. A nice inexpensive-ish option are the AES preamps. I wound the DJH signature for some time and really enjoyed it with some '50's Sylvania 6SN7w's and a Valvo rectifier.