Slint's "Spiderland" album is some pretty epic post-rock if you wanna explore
I was waiting for someone to mention Mogwai - also a very decent band.
Had the pleasure of seeing them in 2009. Very easy to not notice the lack of vocals.
Was this at the Metro? That was one of the loudest gigs I have been to.
I found out about these guys from the Life Aquatic with Steve Zissou soundtrack of all places, and haven't looked back since. Absolutely incredible music.
Even though I'm a fan of a lot of bands there are only a few that give me chills every time, these guys are one of them.