Help me upgrade my PSU

[SmoothJK]

Hi guys, I've looked around the Internet for a solid 30 minutes and I can't find a definitive answer anywhere (I usually can =/).

I have a Gateway GT5252 Media Center PC, which has a 300W stock PSU. From what I understand, it's some sort of weird hybrid ATX/BTW or micro-ATX...I dunno, I'm getting mixed information. Anyhow, I recently installed an Nvidia 9600GT and a Creative XtremeGamer card. Everything is running great, but I JUST realized that the low wattage PSU might cause me serious problems down the road. I'm actually surprised my system hasn't fried yet or something.

I'm looking to get something 500+, but I have no idea how to find something that fits and is compatible with my system. The only info I found of a guy successfully upgrading was a 500W ATX, but that's not really specific enough for me (plus, aren't there multiple types of ATX PSUs?).

Please suggest some specific models that I can use for a decent price. Also, do you guys suggest that I leave my computer off for a while until I put the new PSU in there? I'm starting to get paranoid about my tiny 300W...

Thanks so much in advance. Trying to order today, if possible.

*oops probably should've searched these forums first. Noob mistake...

Couldn't find any specifics in the search. Anybody?

 

[Teny]

im pretty sure the ATX/micro ATX refers to the size of the motherboard.
I had an computer that has an microATX board, and in a small case compared to my cases nowadays.
i searched your computer and it looks like one my friends have, and the PSU looks like the size of the most.
heres a recommended PSU to buy for cheap, and its a good quality PSU too.
Antec Basiq BP500U 500W ATX12V Version 2.01 Active PFC Power Supply - Retail
its 500W, and im pretty sure thats enough for your system.

for those that knows this PSU, and say the OEM one is cheaper, but the OEM is $40 and the shipping is $10, and the retail is $50, and free shipping, so its the same price, and its better to have the retail right?