Ben,
To summarize, I believe that Arcam devices can be quirky, especially their DiVA line. When they do work, they sound great. Despite potential issues, if home theatre audio performance meant as much to me as two channel performance does, I'd probably get the AV9 myself.
It should be very good as a two channel pre-amp, also. I seem to recall a thread comparing AV9 and C31. Try the Arcam Owners' Forum:
http://www.avforums.com/forums/forumdisplay.php?f=119
Alternatively, I might simply go for a Rotel RSP-1098 or the RSP-1068 and look for a good preamp.
I REALLY like my 1098 but don't tell some of the folks on this forum or you might get a nice email flame for even considering such gear!
Good luck!
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