does the fact that its the older generation effect anything? i'm hoping that this will last me a long time
Nothing substantial, the HD7770 will have lower idle power consumption due to its zero-core technology, there's no difference in Direct X technology so the HD6870 will play all the games the HD7770 can with the same settings.
Generally when I make a decision for a graphics card, I sort by all the cards that use a 256 bit memory interface and then find one that is priced right and has the options I want. I've been eye balling the 6870 because it has recently come down in price and has the 256-bit setup.
That will give you such a boost in memory bandwidth and, I think, makes one of the biggest impacts on performance than any other feature.
The 6850 is a strong performer and will cost about what the 7770 does... but then again... its only $22 more!