I'm interested in this sort of riding, but I'm not sure if I can use my only bike to do it. I have a 2011 Surly Cross Check, set up with 48/36/26 and 11-25 rear cassette. I'd be willing to switch my hard skinnies for the 700x32 Ritchey Speedmax knobbies that came stock and switch out the rear cassette for something like a 12-34. Is there any way I can modify what I have for cheap to do some mountain riding? Or do I need to buy some sort of mountain bike?
I've looked into Salsa bikes, the Fargo and the Spearfish but they are damned expensive. I can't do that just yet. I also looked at the Surly Karate Monkey, but the stock is a single speed and I'd want it built up geared. Is there any other brands/models you would suggest?