RE: which motor?
I use Orion revolution V2's when I go brushed mod (# of turns depends on the class you race in). I'm currently using the 11x2 with great results. They run between $40-60 depending on where you get them. For a stock racing motor I will usually go with any PK2 or a hellfire ($30-40). There are lots of great stock motors out there, but its been so long since I've used one that I don't really know anymore. I'm not really sure how hot of a motor you esc can handle (never used a viprer rv15 before) but I suggest getting an orion revolution v2 that your esc can handle. They are great motors and do actually last longer than other brushed motors. good luck