welllllll, first off, you said "mm 4600 sidewinder combo", the mm stands for Mamba Max, which is a different set up than the sidewinder. Based on the price, I'd say you're going for the sidewinder (possibly cc sidewinder 4600 (cc=castle creations)).

Either way, both systems are great. You picked wisely with the 4600, it gives better torque than the rest. You'll probably want a castle link cable to program and adjust the ESC with your computer (lots of cool stuff). I got a Mamba Max shipped to me for $175 off ebay, and the castle link is like ~$20. The MM comes with a USB port, so you don't have to buy the adapter.

Anyway, your call. I know you will have LOTS of fun with it, I just got the MM 4600 in my slash, with lipos.....it rocks, it's awesome with NiMH too, but nothing like lipos.

[youtube]http://www.youtube.com/watch?v=c-6H0vp5HbM[/youtube]

The video is the 4600 motor on 2s lipos.