2GB of RAM won't hurt, but it will only help in a few applications so its not really worth it at the moment... with that setup a 400W will be fine but don't go for the cheap brands.
If your into overclocking skip the 4000 and get a slower clocked venice and overclock it to 2.4 - 2.6 or more (with some luck), otherwise the 4000 is great, and the way intel is stuffing round with netburst it will rule anything from intel for the next six months until conroe arives.