Hi, I'm trying to get my head around the new-to-me shimano levers and shifters. I just decided to upgrade to 10 speed when I destroyed my sram x0 hanger bolt today, rather than wait ages for a new one. (Stripped the bike for a new powdercoat job, but the bugger wouldn't come out; had to drill and tear it out, a real PITA. I think it was because it was torx, not hex, and I wrecked it right off the bat. Doh.)
I'm looking at heaps of used and new levers and shifters and can't figure out which match which at all.
I've got a set of mechanical disk brakes, TRP Spykes. Can all or any of the i spec levers work with any old brakes?
I can grab a new pair of lx levers I like the look of cheap, and found something online saying they're i spec compatible; that's all it says. Is that true? It's these guys: Shimano Deore LX T670 Brake Lever Set at evanscycle dot com.

I'm mostly eyeing a pair (or just a righty) xtr m780 shifters, as I read the xtr lasts a lot longer than xt and below. They come with a normal looking mount, or one or more i spec options. I dunno which lever the i spec ones are meant for at all. Those actually cost way less too, so if I could get some suitable levers cheap, I'd be happy.
Thanks for any help.
Any advice on which shifters have good or bad rep is appreciated too.