Ultimate is a waste of money. All you get is some silly little extras like animated desktop pictures and a couple of rubbish games.
Home is very basic. You don't get any of the cool stuff that makes Vista stand out over XP. It's designed for entry level PCs with insufficient power to run Premium.
Premium is definitely the way to go in my opinion.
I wouldn't wait for Windows 7. That's still quite a long way off.
As to your processor/mobo combination there is something to be said for futureproofing, however the i7 is still pretty much an unknown quantity. The motherboard bioses aren't very mature (in that any bugs won't have been found and ironed out yet) whereas Core 2 systems are pretty much rock solid by now.
Whether you want a dual core or a quad still depends pretty much what you want to do with it. If you do mostly gaming then a dual core E8500 or E8500 will still give you the best results, very few games can make use of 2 cores let alone 4 so the higher clock speed of the Core 2 Duo processors will be an advantage.
If your focus is mainly going to be things like 3d graphics rendering a quad would be better. Bear in mind though that the software you would be using would have to support multi core.