I think you want at least a 450 watt psu, I made the mistake and got a 400 now the next time I upgrade I have to buy a new one.
Also your motherboard, check whether it's socket 939 or 754 because if you get a 754 one, then you feel like upgrading your processor just a small bit, you would have to get a whole new motherboard to be able to take the socket 939 processor if you know what I mean.
Socket 939 motherboards are for socket 939 processors (AMD 3500 and above I think)
Socket 754 motherboards are for socket 754 processors.
You can get an x800 XL with 16 pipes also, that is the one I have. Check overclockers.co.uk that's where I got it from.
