Keep 8800 GTS 512MB or get the new 4870?

I bought the 8800GTS 512Mb a few months back. I bought it at Newegg when they were offering a free copy of Crysis with an EVGA graphics card. So now my question is, should I get the new 4870 and try and sell my 8800 GTS or will I really not see that much of an improvement in gaming and it would be a big waste of money? I have an Asus Maximus Formula motherboard and a Q9450 chip.

I did pay $350 when I bought the card back in January. Would a 4870 be that much of an improvement or should I save my money and use it elsewhere? Any suggestions would be great.

By the way, I love my system now. There are no problems. But I am always looking for ways to upgrade and become faster and more efficient. Would this be worth another $300?

What are your current specs?

Here is a comparison of the two.

Crysis 1280 X 1024 High

4870 = 41.6 FPS
8800 GTS = 32

Crysis 1920 X 1200 High

4870 = 32 FPS
8800 GTS = 20.7

You can see more here

The 4870 would be a vast improvement, but things may change with the 55nm revision of the GTX 200 cards which would enable higher clocks on the cards without a significant increase in thermal output or power consumption. It's entirely upto you what to do, although I'd personally wait for the HD 4870 X2.