So I currently have a nearly 4 year old 4870 1gb that I use in my system. I have been thinking about getting a new card but am not sure as to whether I will see a marked improvement in performance. The 4870 is OC'd to 850mhz core and 1050mhz for the memory. Its runs stable and never exceeds 60*. I see that some of the current 6970's have a clock speed anywhere from 800-850mhz for the core and the memory is slightly higher at about 1200-1300mhz. With these specs being so similar to my current card, is it really going to make that much of a difference if they were both 1 gb?
You can only compare clock speed/memory when talking about the same models or at least the same generations of cards. The 6xxx series is two generations newer than the 4xxx series and uses a much newer architecture. As you can see from the benchmarks the 6970 is two and in some cases three times as powerful as the older 4870.