Getting ready for .5 conversion

so if i were to go w/ a 2s 7.4v instead of a 3s 11.1v would be a good move for my crt .5 cause right now i have 2 6000mah 3s 11.1v, and was thinking bout either try`n to sell them or just use them on something else, and pick me up some 2s ones, just dunno a good mah to get for the setup described above. i was looking @ the 5000mah on 2s, cause that didnt look to bad.