Anyone running a HomeTheater computer?

[vinuneuro]

Been thinking about getting a bluray player, but realized I'd rather have the flexibility of a HTPC. I don't know jack about computers so have had to read for hours the last few days. I think I've pretty much nailed the setup I'd like. Do have a couple questions for now:

1. How important is the southbridge to HD playback performance? I'm looking at two Gigabyte boards that are basically the same apart from the southbridge's. One is 500mhz other 700mhz. EDIT: after reading up on motherboards, it seems that the Northbridge is what handles the important stuff? How much does the Southbridge matter for graphics if you're not using a discrete card?

2.The one with the 700mhz SB is not a micro-atx board. How big a deal is that from a practical pov goes?

How would HD performance differ between a high-end IGP with a high-end cpu like a AMD Quad-core Phenom v. mid-range discrete video card and mid-range cpu like a dual-core AMD?

tia.