associated t4

i've got a t4 race spec and would like to go brushless (mamba of course). i'd like to stay with nimh 6cell packs. what would be the best setup using the stock spur gear. we run on a 1/8 scale track. i was thinking about the 7700 but i've heard it's too much. how is the 4600,5700,6900 any body that has a t4 with the mamba i'd like to hear your opinion's and idea's. thanks.