Your best bet is either the 6790 + 4 GB RAM or just an R7 260x. The thing that the 6790 has going for it is the wider memory bus 256 vs 128, this allows it to stay in contention with the 7770. According to the benchmarks, the cards are a toss-up; both performing about the same. So, take the cheaper card and save your money for more Ram. A resolution of 1600 x 900 is insignificant with most cards now. Most gamers are using 1920 x 1080 or higher.