Substantial difference between 4870 512MB and 1GB for my system?

Hi, I've decided to get a 4870 for my computer, but I'm wondering if there will be a substantial benefit to the 1GB rather than the 512MB for my system. Also, if anyone has recommendations for brands it would be much appreciated

One final question, what is the difference between HD and AX?

Intel Core 2 Duo E7200 @ 2.53 GHz
4GB RAM
500/650 PSU (not sure which one im getting yet)
1440x900 resolution

Sorry, I'm not really computer savvy and didn't think to do that

I checked them out though, seems like a negligible difference.

For ~20 dollars difference, why not go for it just in case your monitor dies and you end up replacing it with a higher resolution one? Or if you replace it on your own or receive one as a gift later, or even decide to try hooking it up to a LCD or Plasma TV with higher resolution? In any of those cases, performance on the 512MB will begin to suffer, whereas it wouldn't w/ the 1GB version.

Yes, the 512MB version suits you great right now, but if there's any chance anything like what I mentioned above happens, ~20 bucks gives you some peace of mind.

Well, in some cases it could be more than $50 difference, but the jump from the absolute cheapest 512MB to the cheapest 1GB on Newegg is like 20 or 25 bucks. To me, it's worth it.

Spend a $100 on an HD 4850 (after rebate and if you are in the US)

http://www.newegg.com/Product/Prod [...] 6814121272

At your resolution and with your CPU at its current speed you won't notice much of a difference between it and an HD 4870.

As far as HD 4870s go there is little to no difference in performance until you pass 1680x1050 resolution. A 1GB card is definitely not necessary on a 19" widescreen. If you don't plan on a monitor upgrade any time soon go for whats cheapest (if your set on that GPU).