Was browsing & saw your question - I've got the same machine & put an Akasa "Paxpower" 12v 2.0 ATX Ultra Quiet psu, 460w. I did have to mod the case (with metal-cutting shears) -the grill at the back of the case for the psu on-off switch to fit, but hey -it works!
Luckily the 8300 is one of the few Dell machines that you can put a bigger psu in.. Look at the wiring loom on the old one & make some notes where they all attach - as the new one has quite a few "spare" leads for expansion etc..
This is the current version:
[color=#0066ff]AK-P460FG-BKV2[/color] at:
www.akasa.com.tw