You could look at the WRT1200AC. It's available as a certified refurb on amazon.com for $90, and as part of their WRT line is intended to support open source firmwares.
Not sure about the 1200, but I have the WRT610N and it has never worked completely with Open/DD-WRT. The best I got (before leaving it and returning to the original firmware) was a functional router but no USB and no 5GHz band.
The wireless driver is crap, though. The last time I checked it wasn't recommended due to wireless problems.