I run Vittoria Rubino Pros on my bike (700 x 23). I get a good deal on them at probikekit.com for about $23. They retail for nearly twice that in most shops. I've had good luck with them in terms of flat resistance (never had one; knock on wood) and I like the ride quality. I think they're fairly easy to mount, too, at least on my rims.

As an aside, has anyone ever suggested running less pressure in your tires? I know it's a personal thing but 120 psi for a 700 x 26 tires, at your weight, sounds high to me. You might play around with the pressure to see if you like the ride quality better at a lower psi, say 100-105. At your weight, I wouldn't worry about pinch flats at that psi. Your tires might corner a bit better at a lower psi, too. Certainly in wet condidtions, I would suggest lowering the psi a bit.