Hoya,
Welcome back to DirecTV. Before you buy anything, test your HR20. Improvements are being made weekly and it also works with Tversity. If you'd like to be part of the community improving tversity on the HR20, send me a PM/email. The interface is not very slick, but it might meet your needs. For the record, I don't use my HR20 but for beta-testing for DirecTV, and not because of limitations - it's just not as user friendly or as slick as the 360. All the music we listen to in our main room is now from the server and it has to be user-friendly for smackette...
I have yet to have a good experience with wireless HD, so if that's the hang up, I'd be more concerned about your network then your media device. If you are unable to hookup your home theater system to a wired network, expect a decent amount of headache. How far from the router is your system? Even an N router one room over can be trouble - it sounds like yours is upstairs/downstairs so music should be fine, but HD movies are going to be tough. Now, when I say HD, it all depneds on your source and if your source files are small (for example, most bit torrent under 4 GB is not full HD), then the G vs. N won't matter much.
The Xbox vs. Ps3 debate is really a preference of games - nothing more, nothing less. There are pros and cons to both systems, but I'll tell you my thoughts on both.
First, the wireless in the PS3 is G and I don't recommend it for streaming HD, though it should be fine for most video content. But for $70 you can get a wireless N and still pay less for a wireless 360 than the PS3. The user interfaces for both are about to be updated, so I wouldn't pay much attention to that right now - wait a month if you can and see what they come up with. I can tell you this, the current Vista Media Center PC on the 360 is the best I've seen though (even smackette likes to use it, and she's not much of a techie at all). If your source computer for most of your media is going to be a Vista MC PC, you should do yourself a favor and at least look at the Vista MC experience on the 360. Who knows what they'll do to it next...
I've discounted all tangible media in my equations, so I won't pay a premium for Blu-Ray (or HD-DVD). I haven't purchased a DVD or CD in over a year, maybe two, relying solely on rental models and downloads. The first company to allow for a $20 license for unlimited downloadable movies that expire (a Netflix meets Xbox Live Marketplace model) has my allegiance for the next 5 years...I agree with Sony, Blu-Ray's dead in 5 years. It's already dead to me.
You cannot add a gigabit card to the 360, but I stream HD to the 360 from my server and it's fine with the 10/100 card (althoguh strangely, adding a gig router made a huge improvement). Yes, I'd like the gig card for faster reading of large Db's (like 40K songs), but it's been fine without.
As for the monitor, sweet. Monitors are getting cheaper because TV's with tuners are now accepting PC's creating competition (and touch screens are the future in the 2009 Operating Systems so the price of non-touch monitors will continue to plummet). It's nice, and as long as you have a digital source like cable or satellite, those are the way to go. It should meet my $400 threashold shortly which means HD for the bedroom (I'm also holding out for Multi-room viewing with DirecTV before going HD in the bedroom).
