You have to think you can get a brand-new leader frame, fork, headset, and handlebars for not much more then $330, so if you think that the wheelset, crankset, and the remaining small parts are worth the extra $350 or so, then do it.

Personally, I think Leader bikes are GOOD bikes, but they are not GREAT bikes. I enjoy riding my brothers and I am debating whether or not to finally build mine (I have a 721 frame and fork just lying around in my room) but there would be no way I would buy one for $700.