Don't get a cheap knock-off ... but consider the e-Power for your power unit, instead of the proprietary, 3.4V battery in the Joyetech. I'm vaping an eGo-T as we speak, but my next purchases (for myself and my friends who want to start vaping) will be the e-Power. Replaceable (generic) battery ($5 vs. $25), replaceable switch, slightly higher voltage - and you can still go ahead and use Joye tanks/atomizers on it if you want to. It might be hard to find in stock right now, so you'll be fine with going with a Joyetech eGo, but I'd get the eGo-C insstead of the -T. Same tanks, but the atomizer section is broken down into 3 pieces: base, cone, and heads - the heads being the electrical guts of the atomizer section, which can be replaced for about 5 bucks.
(I have a 1000-mah Joyetech eGo passthrough and 2 1000-mah "batteries", and they're fine, but replaceable batteries are the way to go IMO. You can have a bunch of them all charged up and ready to go, instead of having to tie up a power unit every time the battery needs charging. Among other things, that means that you can always have one additional flavor in your rotation).