I would watch that 5000mah pack from truerc in that setup. They have good packs for the money, but most run the 8000mah pack from them cuz they are only 10c and 15c cells and the bigger capacity allows more current handling. I think the 5000 cells from them are 15c which means 75A current rating for that pack. 6s in my revo with a 1515/2.5d pushes the true rc 8000 cells. The 8000 packs are good for 80A continuous so its not that much higher, but just watch them you will be pushing 15c 5000mah pack pretty hard. You will probably be fine as long as you dont go crazy with the gearing.
ANd I agree with everyone else the 1515/2.5d is a perfect motor for a high powered 6s setup. Hope you have some upgraded difs.