Hi i just picked up an quad core gateway computer it has an Q9300, now the power supply is only 300 watts with 14amps on the 12V rail, now the power supply seems to use a 20 pin connector to the motherboard and theres no 4 pin connector to the cpu this is the first time i have seen that i don't know is that matters or not, what video card can i use right now theres a ati hd 3450 and is this power supply normal or what
Exactly what model?
What are you doing/want to do with the system?
AFAIK all the new systems need at least a 24 pin for the MB plus 4 pin for the CPU, I'm not calling you a liar, but please confirm the wiring configuration.
Given the limited power, I'd say the DDR3 HD4650 is as much as I would want to install-but it's a weak card for games and if you want or need more graphical clout, you'll need to install a bigger PSU.
For HTPC use the 3450 might do, if not the HD4550 has good Hd/DVD decode.