I just replaced my GTX 640 which came with my i3 (3220) X51 R1.This card works great. It uses a 6 pin extra power connector which the X51 has. I first ran it stock with no problems on benchmarks like Cinebench, 1320 boost clock gave 70.89 FPS. I then pushed it by adding 82 MHZ boost and +386 MHZ memory. This produced a 1402 MHZ boost clock and 5396 memory with a 86.3 bandwidth. BEWARE the X51 heats up quickly to 65 degrees C.Valley benchmark says it is at 1582 MHZ. I can say that as long as you do not push overclocks too far the EVGA FTW card is great for a 330 watt X51.