If I was forced down to one bike the crosscheck would be it. Don't know about the other choices but you can (and a lot of people do this - search velospace.org for instance) make it into a fixed gear/singlespeed with its horizontal dropouts, ride it offroad (almost a 29'er with clearance to 700x45), commute, and tour with it. Lowrider racks will mount onto forks without the braze-ons, it's just not as elegant. I did this with my mountain bike. It's not the perfect bike (could be lighter, that fork is very heavy, 4130 tubing) but it is easily the most versatile bike I got and I got a lot.

There is a fairly recent review of it at fixedgeargallery.

I built mine from frame up so it's got a triple crank, mismatched brakes (front vbrake, rear canti), 7-speed barends (friction!), etc. It cost about as much as buying a whole bike except I had most of the parts already and the big cost to me was having a rear wheel built by the local shop. I think $700 is fair is that guy has significant upgrades to the build. Otherwise you can buy new for about that much online.