I think that the Steamroller is going to be out of your price range. If that 925 fits, do give it a good, looong test ride- it gets much love in BFSSFG here (and elsewhere), but is no longer in production .

As far as tire sizes go, the smaller the diameter of the wheel, the faster it accelerates and generally more nimble when turning. Drawback is that they don't maintain the speed very well given the same amount of effort compared to larger wheels. But if you're going to be riding in very population dense areas...

As far as best bang for your buck folders, you might ask the folks in that forum.