I used to have a Stampede with a 12s running on 12 NiMH cells. Top speed was about 55 mph, so you should be able to go 30mph on 2s. IMO the 12s is a great motor for running up to 4s in a rustler/stampede.
I now have a 12s on 4S in my rustler and so far I like it alot. Its geared 17/87 on M2Ks (little undergeared I think.)
It does low 50ish I think (snagged a curb before I got to radar it. No big damage tho, just needs a pin.) Amp draw peaks at ~60A at the current gearing for a comfortable 850-900W. Controller stays cold and motor so far has not got too warm, even in grass.