Ok, the 1515 1y on 6s lipo is a bit much, you may have issues getting the gearing right. I would suggest 5s lipo, around 5000mah and at least 25c rating. Neuenergy, flightpower, and polyquest all offer packs like that. You could try the elite cells, but I have no experience with them. The 1515 1y will need a good lipo to perform, but you should be able to get the right pack for less than 350.
This is what I would run:
http://www.hobbycity.com/hobbycity/s..._5S_25C_Lipoly
Or the similar pack from neuenergy or flightpower.