Replacing an ATI Radeon 9800 Pro 128mb AGP graphic card

I have a 2003 Evesham Axis 3000 system (AMD Athlon processor).
Graphics card is an ATI Radeon 9800 Pro AGP 128mb which has just
packed up (out of warranty of course).
Should I replace it with the same card (can be had on ebay for £30 to
£40 second hand) or should I go for something more modern eg Sapphire
Radeon X1650 Pro AGP 256mb.(£53 from eBuyer).

I am worried about the Axis PC's PSU capacity (320w I believe?) to
handle the more up to date and more powerful graphics cards.

Can anyone confirm the capacity of the Axis' PSU (I can't tell just by
opening the case and am reluctant to disassemble the PSU).

Also I have heard that the Radeon X1650 can get very hot - not sure my
Axis case is that well ventilated. If so, what other cards could I
consider?

Grateful for any advice.

Gordon