Inspiron 545 power supply

Inspiron 545 with intel q9400 quad core, 8gb ddr2 800mhz ram, ati hd5670, 750gb hd, single dvd muti-layer drive,soundblaster audigy 2 sound card, however I would like to beef up the video for gaming if possible,also I'm running windows 7 home premium if that makes a difference
 

I did some research on this psu, and I love it, I'm considering selling my dell and doing a custom build, however I will need advice on a good crossfire capable motherboard, case, cooling options? etc, also it would be great if the mobo could hold a max of 16 gigs of ram, I love expandibility!