i bought a GSP katana last week with moki 180 and it's almost ready...

i just have to buy a servos for it, and i don't no what servo to go...,
i don't have allot of money for the servos (250-270$) so i think about hitec servos, i saw the 645 but it slowly... (0.24 sec).
and i saw too the 625 but it little weak (77 oz- it will be enough for the katana?).
thanks, Weinstock.