Recomend a PSU for this system???

None of those parts are even failry new, get the cheapest 350w PSU you can find.

Okay, start by deciding what features you want: Active PFC? and types of connectors you'll. If you have a tower case, length of cables also factors in. And you're definitely spot on with a 300w-350w psu.

Suggestion.. visit NewEgg. Pick out what you want..very easy and always read the customer reviews of each psu that interests you.

Choose a good brand : Antec, Enermax, Fortron, Seasonic, OCZ, ect..

If you want to clear out cables in your pc then this is a good modular psu (athough it has issues with Asus mobos - may have been corrected by now):
Antec NeoPower NeoHE 380 ATX12V 380W
It's designed for new pcs ($80), but is compatible with older systems as well.

Antec SmartPower 2.0 SP-400 ATX12V 400W
More power than you need, but it's worth a look. ($55)

FSP Group (Fortron Source) AX400-PN, 12cm FAN, version 2.0, 2 SATA, PCI Express, 400W Power Supply ($40)

All the above have 120mm fans so they are fairly quiet. Another good place to shop is ZipZoomFly... prices and customer service are great, but they don't have the excellent user reviews like NewEgg.