Actually, your $5000 budget wouldn't cover it.
He's the deal - any of those receivers would be fine choices - you can't make a mistake. Also, some of the mid-upper end HK receivers would be OK as well. My personal choice would be the Denon 3805 because of the price/performance/value relationship and because of Denon engineeering. I like Denon. Go to the manufacturesrs websites (or Crutchfield) and look at the features of the units you mentioned. This will boil down to the features you want.
Also - have you talked to Axiom directly? If not, you should. With that size room they might suggest that you move up to the M80. I think the M60 would be OK, but they do this for a living.
You might also consider a1) the EP500 sub or 2) an SVS (25-31 PC+ tuned to 20hz) or HSU VTF-3 sub, also tuned down. You will be filling a large room with LFE and want to be sure you have enough sub. "Almost enough" is VERY disappointing and is the difference between a subwoofer and a subwhimper.
You should be able to come in well under $5K, unless, of course, you buy Mark a very expensive gift. I'll send you my bill in the morning.
