Amp pairing questions

I’m thinking about purchasing a pre-owned Pass Labs XA30.8 amp (fits within my budget) but have some questions.
My system includes:
Cary Audio SLP70 tube preamp
Chapman T7 speakers (90dB sensitivity, 4ohms impedance)
Will the XA30.8 be compatible with my preamp and speakers?
Now for a question that will surely show my lack of knowledge.
The specs on the XA30.8 state power output at 30W into 8ohms and 60W into 4ohms. My assumption is that the amp detects the impedance of the speakers and produces the output based on that. Is this a correct assumption? 

Showing 1 response by z32kerber

Thank you all for the great advice and education. MUCH appreciated. I think I'll go ahead with the XA30.8. I'm certainly not a headbanger person. Mostly jazz and some pop.