thanks. yeah the thing is, the 725tr is designed for tricking so it's not going to be much lighter than a kilo, especially if you don't use expensive components. you'd be better off with a 721 or whatever... just because it's aluminum doesn't mean it's lighter. they have to use more aluminum to make it strong enough and cheap bikes aren't going to be light and durable.
you'd be better off putting the money into a nice wheelset, that's where a lot of weight is... and it's rotational weight so the savings is much better felt because you're not turning it. rotational inertia makes wheel weight savings way more beneficial. and if it's hills you're having a problem with, you might want to just adjust your gearing or get bigger muscles.