oh... I can't believe I didn't see it the first time.
anyways, even 30-35 is no problem with the 3700kv. you can do that on 3s with mild gearing. On 4s, you're going to be in the 40 mph range with normal gearing.
I run the same motor on 2s & 3s in a M18T. I'm geared at 14/54 right now, and I'm guessing low 20's on 2s and low 30's on 3s. These are perfect numbers for mini racing... unless you're on a 1/10th scale track.
There's two sides to every schwartz, he got the up side and I got the down side.
I would keep with 3s honestly. In anything but a tiny 1/18th you will be pushing it really hard on 4s. If you want 4s you should step up to a larger ESC, the m25 just gets hot on that high of a voltage.
4s may be too much for the internal bec, so 3s may be a better choice. Unless you want to run a ccbec, but that seems overkill in a 1/16 buggy. Unless you have the batteries laying around. That hacker motor is nice, I had one in a minit for a while and ran on 3s!
My quark stutters on 2s in a mini t. I can't figure it out. I thought it was just a bad quality battery. I now have a better lipo in it and it still stutters.