hi i was going to upgrade from my 8600 gt ddr2 512mb gpu i was looking for a suitable alternative within the price range of £50-60 if cheaper better my pc specs are e6750 2.6 ghz cpu, 4gb ddr2 ram @ 800mhz, maximus formula motherboard ( i wont be overclocking btw) , and a corsair tx650 650w psui would be playing games on 1680x 150 resolution and high if maybe full graphics AA is not important to me games i would be playing is empire total war , napoleon total war, and shogun total ar and some FPS like BF3
It will be a bit better, but your going from a mid-range obsolete card to a budget modern card, so don't expect a huge difference, newer cards are faster but you're also looking at a lower tier card than what you have; I personally would expect a rather small improvement (though I wouldn't really be surprised if it were actually worse or the same)
I would wait until you had a little extra budget to get a card closer to 150$ or so (7770, 6870, or nvidia equivalent), personally. It's just not worth upgrading to something that low-end unless you want to play games at bleh resolution and quality.
However, nobody can really say quantitatively how much better one would be than the other, as the old cards don't have benchmarks for modern games, and modern cards don't have benchmarks for older games. I can tell you my wife's computer recently got upgraded from a 8600 to a 7770 and it made a big difference in performance for the Sims3
Also, as someone above said, your playing rather CPU intense games, so you may be bottle necked by your older CPU if you get a better card, but it should still allow you to turn up some of your graphics options like Anti-aliasing, shadows, reflections, etc if you keep cpu type settings low (like persistant scarring, dead bodies, clutter, physics, etc) and give you some nice benefits.
hmm yh i think your right i have had second thoughts on buying that card even though i will be getting it really cheap i think it is better to wait a little while and who knows may be prices will go down. thanks for the help all.