That battery will provide 50a of power continuously. (2500x20/1000=50) With a mild brushless combo, it'd be good for about 10 minutes of racing. For the sake of extra run time or more consistent performance, you could go up a notch and stay affordable. Don't recall if you're running v1 or v2. If you running v1, I think there are some rounded packs made by "Peak Power" that are around 3300mah and have a decent C rating. I'm using a v2 and have found the 4200 Turnigy Nanotech shorties from Hobbyking very good. Cheap and the C rating is huge, compared to what you actually need.

Think of it this way, even with a 13t Hobbywing system, you're unlikely to ever need more than 35-40a power. Either battery is just the right amount of overkill. overkill.