I’ve ordered a graphics card based on the Radeon 9500 PRO circuit and I’ve begun to wonder
how much power it’ll consume and if my current 300W PSU will suffice. If not, I’m curious if
this chassi with this PSU could be my saviour.
Any ideas?
It depends.
It depends on what else you have in your computer running. If you have 5 case fans, fancy lights, 2 Hard Drives a Cd-burner and dvd-rom, a processor that takes lots of juice to run, etc, you will probably need a new PSU. If not, who knows. You (and us) won’t know until you plug it all in and start (or dont start) haveing weird things happening and random crashes. To be on the safe side you should probably get a new PSU(although I wouldn’t).
From the ATI site:
You already have a 300 W supply, so should be no problem.
Thanks for the very swift answers. I suppose there isn’t much to do but to go by trial and error. Thanks again. 
300W may be sufficient, depending on what other hardware you have installed, but not all power supplies are created equal. This article from Tom’s Hardware is a good read.