i was in the exact same spot about six months ago when i upgraded mine, and honestly that 500w power supply definitely wont cut it for a 7800 xt so youre right to look for an upgrade. i grabbed the Corsair RM750e 750W 80+ Gold myself because it fit right into my tight budget at the time, but fair warning about that fan noise you heard. it mostly stays super quiet under normal gaming loads, but whenever my system hits a heavy spike, that fan spins up and sounds like a tiny jet engine for a minute. if your pc sits right on your desk near your ears, it might drive you a bit nuts. i would suggest checking out the Thermaltake Toughpower GF1 750W 80+ Gold instead if you can find it under ninety bucks. a buddy of mine has that one and his rig is way quieter than mine, plus it has been rock solid stable. just make sure to double check prices on newegg and amazon because they fluctuate like crazy every few days. whatever you do, dont cheap out on some random no-name brand just to save twenty bucks, because fried components aint worth the risk. grab a solid tier b or tier a unit and youll be totally fine.