If you go with a Major OEM like DELL get Vistal Ult or Business an then do the windows XP downgrade to PRO.
That way when they say things in VISTA are looking better you can change back.
I would think you would have MUCH MORE fun building your own box.
I LOVE AMD... I have always bought AMD but lets face the truth. They are behind. WAY behind. Look at all the news stories on the net. They are cutting jobs... developments have come out way behind... I think AMD is gonna end up Bankrupt and have to do a reorganization...(not good for us consumers).
I agree with the previous threads on MSI motherboards. Getting support and updates from MSI is great. How ever, there are some VERY GOOD gamer rigs and over clocker boards.
MSI has a killer Diamond board.
ASUS has one called Crosshair (a tad older but powerful)
there is a million choices.
And of all the advise you can get,.... what ever you do.... dont buy "cheap" generic RAM.
http://www.crucial.com is your friend. They offer LIFTIME warranty.
once you pick out what you getting post back your results!!