Well it looks like the 550watt is only $40 more expensive, so thats definately an option right of the bat (at purchase time). So thats definately advice i need to take.
And unfortunately the 512MB 7900 is $250 more than a 256MB, I can't justify that atm for a video card. Im not looking to run games in 2048 x 1536 yet (will need a new monitor at the same time), as the 256MB (7800GTX / 7900GT) runs the games im looking forward to in 1280 / 1600 with 60+ fps.
Im actually just looking to be able to play battlefield 2, HL: Source (and related), FEAR, Elder scrolls and a few more games.