Well, there's so many options out there but most would say to get an ego or riva:
Ego-
Electronic Cigarette - Starter Kits - eGo
Riva-
Electronic Cigarette - Starter Kits - Riva 510
I'd say the Riva has a little edge over the ego because it's regulated at a slighly higher voltage (3.7v compared to 3.4v) but they're essentially the same.
The 650mAh
batteries last me all day and it's really not much bigger than a superking, just fatter:
http://img.photobucket.com/albums/v233/leftfeild/capon.jpg (ego next to a volt pv)
Click the discount code on the top of libertyflights for 10% off as well!
By the way there's also a 510 to 808/901 adapter out there too:
Mods - E-Cig Multi Adapters That way you can keep using your 901 cartomisers or try out the many, many options a 510 threaded device has.
I use the ego with an 808 adapter so I can use 808 cartomisers on it and still use my volt with its 808 cartomisers. I save money just buying one set of cartomisers this way.
So yeah, all I'm saying is you don't need the whole kit, if you want you can get a set of
batteries, a charger and an adapter and there you go, compatable gear that's going to last a ton longer in battery life, though it wouldn't hurt to get a whole kit for the atomisers and stuff that comes with it. More spare things to keep you going!