I take back what I said, I didn't realise the 6450 was a very low power usage card. even under load it should comfortably stay within your psu limits. apologies for misleading you.

@therepublic

You have a Dual Core ? Your data sheet says you dont.

Brand: Intel® Pentium® 4 processor 820 Speed: 2.8 GHz 800 MHz front side bus 2 MB L2 cache


If you really have a Dual Core you could still squeeze out more Power with a better GPU.

If your PSU wont meet the demands it wont work at all or be unstable. But a 6450 will work it needs 25 Watt under load.

This can be useful, but you must get further infos about power consumption.
http://www.tomshardware.com/reviews/gaming-performance-radeon-geforce,2997-7.html
If you find more than one GPU that stay within the power limits of your PC, the chart will tell you which one is faster, then you just need the price to decide what's worth more its money. The chart tells you also whether a card will give a noticeable boost, it must be at least three tiers higher than your current one to do it.

My current is the integrated Intel GMA 950.  That is only one tier up from the very bottom of the list.  Just about anything is an upgrade.

In this case you'll have one less thing to worry about!    I had a Radeon 9250 years ago, 5th tier from the bottom, and I felt a nice boost with a notebook with AMD M690T chipset (X1270 integrated GPU) and an almost huge one when I upgraded the desktop to a MoBo with integrated HD3300 graphics, go figure... In the mid term I'll need another upgrade too, when my backlog will shift to newer games and I'll buy the Witcher 1 and 2 and other recent games in my wishlist.

I went ahead and ordered the HD 6450. Thanks for your help! I'll let you know how it works for me.

Card installed and working great! Thanks for your help everyone.

Now I can finally play Portal.