I know what you mean, but it's $100 difference in the context of a ~$3k rigid single speed. Just get the frame you want.
I think they're coming out with a TT ox platinum ragley TD-1. Should be about 2000g.
I have a lynskey roadie. It's awsome and all, but i'd spend my money differently next time I reckon. If you're getting a bike that'll last 10, 15, 20+ years, save your money and get something off the hook, as opposed to a fairly budget titanium frame.
Also. The El Mariachi is super good. Geo is spot on and rides intuitively, rear and tracks well (I reckon those dropouts are about as laterally stiff as a house) but still has the "-5psi" ride of steel frames. Heavy tubes mean you wont dent it. Heavy (12kg sus-forked single speed as I rode it) but would still build to a sub 10kg rigid SS (I have the spreadsheet to prove it) and it is my favourite colour.