I think you should contact Reno HiFi and arrange an in-home trial and bypass
the speculation.
I also think John Devore has already mentioned what amps he believes would
work well.
In my system and room (93dB speakers), the XA-30.5 was very close, but
wouldn't quite get the job done in the volume department. If you audition the
XA-30.5, you'll know how the XA-.5 series sound on the Nines, and then you
can move up to more power if necessary.
IMO, any of the XA-.5 series Pass amps are better choices than the X-350.5
because of their more refined sound.