If you can find a good deal on an m4 or an 840 i highly recommend it. I picked up 512gb m4 for 300 during black friday and a 512gb 840 for 320 last month.
@Tomislav, hyperx 3k should be fine. the fact is this: there are many decent ssds out there; and most of us recommend them based on personal preferences and experience only.
as always tnx rewben, samsung is rather expensive here (almost more than 200 $ for 128 GB) and I'ver read the benchmarks for kingston and they score almost as high and even higher in some categories as samsung 840 and it's 20-30 $ cheaper.