Hi David
Welcome to the forum.
My vote would be to get yourself a 568.2mm processor. ridiculously good value on the used market these days (about �900 in the UK) it was a �4350 machine in it's day, and IMO is only bettered by the 861v4.
No room correction to fuss about, handles full analogue systems as well as digital, can accommodate the HD621 add-on box which will give you the newer BD codecs. And most importantly...sounds gorgeous. You'll pay twice this on the used market to get a G61 or G68 variant processor, which add more features, but also complications if you want full flexibility in terms of the downstream kit you use.
Audiogon would be a good place to start looking.
Cheers
George
PS there's also the 568.2 (not 'mm') which sounds identical but will cost a bit less, but it lacks the 'mm' expansion port for the HD621, so none of the high res Bluray codecs are possible with it.