Explain the motors?

What are you trying to run this in. A 2S lipo pack isn't much voltage and with the 2.5d and a good battery pack, you're only looking at about 14,000 rpm. It's gonna be a dog, unless it's some type of crawler, in which case it'll probably be too fast.

Is this going in a 1/10 or 1/8 scale? If you're talking a Monster truck, like an emaxx or revo and two 2S2P battery packs, then the 1512/2.5d should be a nice motor to run with the quark.