Can someone Help me buy lipos for my first setup?

[speedemall]

Okay I just finished a brushless Inferno gt running single pack configuration,MMMV3 and 2200 KV.Can you guys recommend the type of pack I should run on this setup.Someone told me to run a 20c 3s pack but this just doesn't seem like it will be enough being that I want at least 15-20 minute run times. I checked hobby city after hearing so much about the zippy's but they are all sold out. I was thinking of going with their 5000mah 3s or 4s 25c packs. All of the other brands of lipo seem overpriced everywhere else ,or am I just being cheap? lol