HKPC and media server build check please...

Looking to buy within a week a home media server setup from scratch. Along with that functionality, I need it to directly run an outdoor speaker system amp. With that in mind, direct sound output is mandatory which is why I didn't run a Windows Media Server off the shelf. I also like the HDMI output of the listed MOBO but only really need it when I upgrade to Blueray in a year and run my kitchen HD panel directly from this unit (don't have that yet but I'm calling it a HKPC).

Wanted functions in order:
Remote backup location of multiple other PC's in house
Basic audio out to an amp is a must
Media storage that can be expanded with relative ease w/ some form of RAID.
Under $600 to my door not counting OS
Quiet

1) Which OS exactly will suit me the best for the majority of the things listed with relative ease? I was assuming Windows 7 Ult 64
2) What hardware should I change out? I just whipped this up today so no sweat swapping out anything.

2x
HITACHI 0A38016 1TB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive - OEM

I liked the HDMI and plenty of SATA
GIGABYTE GA-MA790GP-UD4H AM3/AM2+/AM2 AMD 790GX HDMI ATX AMD MOBO

I had no clue here...
XCLIO STABLEPOWER 500W 500W ATX SLI Ready Active PFC Power Supply

Low power=cool=quiet?
AMD Phenom 9350e Agena 2.0GHz Socket AM2+ 65W Quad-Core Processor Model HD9350ODGHBOX

Uhhh...
Rosewill Conqueror WBK Triple 120mm Fans Steel ATX Mid tower Computer Case with Side Panel

It was cheap...
Kingston HyperX 2GB 240-Pin DDR2 SDRAM DDR2 1066 Desktop Memory Model KHX8500D2/2G


Along with a free 8gig flash drive it all = $531 today

Please help! I need the backup function sooner rather than later and I would beat this to death myself if I wasn't in a relative hurry.

Thank you for your time.

I do happen to have a brand new extra black microwave with a coffee maker built in I might be able to mod

I do want remote desktop for sure. I should have added that, sorry.

I also do have a server 2008 lic floating around but I figured the vista/7 path was more media friendly but I didn't think of business having the media functions Ultimate had.

I will look for new drives and at other cases, TYVM

Now that I think about it, I have the antique floorstanding radio from "A Christmas Story" I was saving for a "magic genie/8-ball" mod I can use too, that might be cool for this and that.........

Sucks I won't have the Media Server function until 7 upgrade though. Still seems like the smartest plan though which saves a few $ and that aint not bad.

That box doesn't have enough internal SATA slots but the proc/mobo looks nice. I only looked at the 4 core to start based on the low power.