Downsizing: Separates>Integrated --PSAudio>Pass Labs

If you have to go the integrated route, then the Int250 is most likely one of the best choices. But I think you understand that going from monoblock amps and preamp to a one box solution involves making compromises. 

I would look for a Gryphon Diablo 300. Virtually no compromise compared to what you have today and albeit relatively large and most definitely heavy, a single component that can makes downsizing very palatable.

Thank you

Unfortunately the Gryphon is just out of my price range but it does look awesome 

you don't mention your speakers or your space... but pass integrated should be just fine, how it will compare sonically will depend somewhat on what tubes you used in your bhk300s