Sounds like you are on the way ! 10 speed Cassette and chain are not a huge expenditure for Deore/SLX level stuff and not too bad for XT level either. Hope the bike looks good for ya.
Personally, i love the idea of a light and simple rigid bike and am considering having a local custom builder tig weld up a 29'er single speed frame --- but i havent ridden a rigid bike seriously since i jumped to dual suspension a few years back.


Once you get yours setup - whatever you decide on --- then it sounds like you have to get one for the GF too --- that might be 3x as complicated