Which high-end receiver?

If I'm not mistaken, the Macintosh is an analog multich channel preamp, right? If so, you can forget dynamics for movies. You're then relying on the processing in your dvd player and other sources, and your not getting the gain you need for proper dynamics and such..my experiences anyway...and that's a lot.
I could be wrong on the Macintosh, but I don't think so.
What speakers are you using anway? Makes a differnce.
Yes, receivers ARE NOT as good sounding as good separates, and usually not as strong overall, depending. In short, you'll have some compromises often.
Still, what has been recommended above, and what you're considering are, yes, the better receivers. Older 5.1's that sounded pretty good are Arcam's, Sony 777es, Nak AV10, Marantz SR14/18/etc, Denon 4802/5803/yada yada, Yamaha RXV1/DSPA1 and such.
Still, I find no "super receiver" that's going to replace good separates anytime soon. But you can do bass mananagement on these to help your power and dynamics, and at least get descent sound with the right piece, yes.
Might consdier the sunfire piece...heard it once and it did sound promising overall.

I think people should find out what's the real difference between good separates and receivers. If you take the Arcam, and put it up against some modest separates (budget even), you'll find dynamics is a huge factor, in favor of the separates!...my experiences mostly anway.
If you're willing to sacrifice dynamics, even at low volume levels, then I think you can find a lot of receivers that offer a good level of clarity, detail, and resolution, speaking stricktly of sonics.
I have yet to hear any receiver that can deal an acceptable level of dynamics for movies or music!
Given, when I go to a movie, the real passion, drama, and heart of a system is the dynamic level of realism it portrays. And I think most systems fail here. So, receivers are already dynamically short on "the goods". It's hard for me to give in this area personally.

"...the IAR review of the AVR300 is the strongest recommendation of a product I have ever read." (Obrown)

THIS MEANS ABSOLUTELY POSITIVELY NOTHING!! Infact, what am I thinking? I should be driving my Wilson's with the AVR300!...yeah, NOT!
I've been in/or around the audio/video high end biz since the early 90's. I've worked in 4 high end salons, and 2 higher end chain audio video stores in that same time. I've sold just about every concievable product you can imagine, and have kept tabs on reivews and ratings in the hifi rags in just as long. let me repeat: (as, yes, I've read (it's like reading the inquirer...it's just teasing and stimulation really) the Arcam 300 review) THESE BIASED REVIEWS ARE SIMPLY MARKETING HYPE, AND PAYOFFS FROM MANUFACTURERS!...I garantee it! I've seen it time and time and time again.
Now, as receivers go (limited), yes the Aracam receiver is probably a good receiver. I used to deal in the original model 100. But, it's just a receiver. Reading this review is reminiscent of all the other overhyped reviews I've come across over the years in Stereophile, HT magazine, Stereo Review, SGHT magazine, and others!
Case's in point: All Def Tech and Paradigm speakers are rated as mostly "State of the Art" by mag's like HT. Stereophile Rates products like Adcom GTP750 preamp, B&W N805's,Bryston 9b amp, and such "Class A"...yeah right. I've sold all these, they are not super special. Someone got paid off to write shinning reivews. And for the record, there's never been any Bryston product worthy of "Class A" IMO.
These are just examples (others like Sony EP9es dd/dts pre and B&W DM302's in "class B" Stereophile). Ofcourse many such products keep slipping down the totem poll quickly...this way they can justify their claims of "over-zellous" reviews, and say they were mistaken later on. Baby, it's definitely about the money, and selling product.
So, anyone here who'd like to think in their convenient imagination that the Arcam is the best thing to happen to audio since the advent of the speaker, reconsider!
The Arcam won't be replacing most any good separates anytime soon! It's a receiver...like the Denon 5803, the Marantz SR14, the Yamaha stuff, etc. They're just receivers. Nice for what they are...not as dynamic and resolved as better separates, among most other sonic area.
You can take the Arcam down off the pedestal of worship now. Trust me.

You know, I've not totally kept up with what's sounding/performing these day's in the lower priced pre/pro's. Thes Outlaw 950 is a clean detailed piece, but is only a tad more dynamic than the typical receiver as a pre. Don't know why, it just how it is. It's good stuff for the money however, and good investment for cheep. The NAD T643(?) or Adcom 860II I've not auditioned, so couldn't comment. Might be worth a try, and probably a better choice with a good matching amp than any receiver for the same money. I'd be interested to see how they perform.
Right now I'm using a budget system, and am doing a small but extremely potent and well balanced Infinity Beta 10 speaker system rith now, with dipoles in rear, and 3 Athena ASP400 powered 10's in a small 11.5x9' room. I'm using both the Acurus Act 3 and Krell HTS 5.1 digital pre's-of-old with the Acurus 125x5 amp, Panasonic DVDA310 dvd player, Monster power surge, harmonic truth link IC's, and (my secret cheep weapon) Home Depot sprinkler wire for speaker wire!!!(shold not sound as good as it does for cheap, but it does).
I'm using this only as HT system, but will likely add a good 2 channel pre to the mix, with SACD/upscaling dvd player option later.
Right now my sound is so dynamic, clear, and potent, I couldn't be happier for movies. It rocks indeed, and sounds great at low volumes as well.