Advice on a new Video Card

where do you intend on buying from? I see you're in the UK , so I'd like to get an idea of what you have available and pricing

For your money i'd suggest looking at a 1GB 4670 which should hit your pocket for between £60-£70. A 512mb version would be fine, but depending on the resolutions you intend to run it at, more memory is better. It will also give you a year or two before requiring upgrading again.

Have a look here at scan's website, they do some of the best prices (just order online! Queuing up there takes hours )

www.scan.co.uk

I currently have an 8800GTS 512, it was the best card in terms of performance for price about a year ago. No idea what the current standard is now, but the card can run Sins on full detail with mass fleet battles so I'm hoping it can handle Demigod.

Let us know what you decide on

It really depends on what resolution you're running and what settings you want.  A Radeon 4830 will run at around 1680x1050 high settings buttery smooth, and costs around 65 pounds.  The 4670 mentioned above will be a little bit cheaper but much slower, I wouldn't save that money for that much of a performance drop personally.  If your running only 1280x1024 than it might make sense to go that route.. If you can find a Nvidia 8800gt or 9800gt for a similar price, it would be close in performance to the 4830, perhaps slightly better. 

As you may have already figured out, it will definitely run Demigod pretty well.  8800GTS is still pretty respectable, there are a handful of faster cards but it will run almost anything at 1920x1200 with reasonable settings.  Just games like Crysis require more.

You might be able to get a used Radeon 4850 within that range if you feel you badly need something better.

Oops... I mixed up posts here... Edited to make more sense.

I use a GeForce 8600 GT, it has 512 mb of RAM and a 540 mhz gpu and runs any game. You could probably get one for less than £70, cheaper if it's used. It's really great value.