Yes it will be discontinued but its performance is great for the price. It is a better card than the 4890 by a bit, but if you overclocked the 4890 you should be able to hit some nice speeds. but the 4890 is a much better buy for the money and the performance difference is not much, i was suggesting the gtx280 just because it is much cheaper than the 280 and you were close to budget.
12GB is the most you will ever need anyway, other than the max memory i would say the only difference is the P6T would overclock better then the LE but around the same as the EVGA A1 on air. Personally i think the best choices for you are the p6t v2, gigabyte ud4p or the evga A1. From those i believe the ud4p is the best. You havwe to understand most of the good motherboards like these will overclock just as good as any other board but they limit bios options and motherboard cooling mostly which they save for the extreme boards.
12GB is the most you will ever need anyway, other than the max memory i would say the only difference is the P6T would overclock better then the LE but around the same as the EVGA A1 on air. Personally i think the best choices for you are the p6t v2, gigabyte ud4p or the evga A1. From those i believe the ud4p is the best. You havwe to understand most of the good motherboards like these will overclock just as good as any other board but they limit bios options and motherboard cooling mostly which they save for the extreme boards.