both my guitars hadn't been looked after properly, a seven string Ibanez gio which I did have serviced and a bc rich beast NJ which I resoldered myself.

I'm still unhappy with the feel and performance of both. they are ugly and uncomfortable. Not sure if that is because of the way they are set up with the truss and other issues or just because they are cheap.

This makes me think I'd be better off investing a high quality guitar as I think both of mine are crap. Yet I still feel I should do my best to restore these two that I have. If not to keep but to sell.

don't get me wrong, both guitars have thier good points and I'm sure, with enough mods, could get some satisfaction from them. But because they are cheap models, I think that is where the main problem lies and THAT can only be fixed by buying a more expensive guitar.  
Sell those guitars and get a new guitar, make sure you try every guitar in your interest before deciding.Had the same issues,sold my oldies got a new one.
Sell both, save some extra money and buy the best possible guitar you can. It will increase your motivation and speed of your skill improvement.