Depends on your proc. For the 920 you have here, I believe you must have tri-channel. In fact, tri-channel is generally better, as it leaves more room for expandability down the road, usually up to a maximum of 24 gb (6 x 4 gb). For the 750, you need dual channel, which is an older configuration. The 920 is generally much better, though. In fact, I can't remember a single test in which the i7 bested comparably clocked P55 i7s, to say nothing of the X58s (like the 920).
No, get rid of it. It's very low-end; in fact, IIRC, its a rebranded 8800. If you can, wait a few weeks, because nVidia is expected to release the GT300 series, which should lower the prices of the 200 series, and let you get a graphics card worthy of the name. Everything else looks good.