two things. 1) you need more than one battery. really. you will get frustrated and bored with only one battery pack. 2) since you are using the hs65mg servow (yea!), see if whoever you buy the dx-7 will let you buy the package without the standard servos and the receiver battery. when i got mine the hobby knocked off aobut $75 - $80 without the std servos and rec battery.

have fun and enjoy the new heli. i've got nearly the exact same setup you describe (but i am using the align motor and esc). currently have 3 battery packs and my wife is bringing me 3 more packs from united hobbies in hong kong. of course with more packs you probably need an additional charger. the cellpro 4s is a great charger for around $60 (but you may have to spend another $10 for a connector to fit your battery).

gw