I'm considering buying one of the Marantz SR receivers (SR5007, 100 wpc; , SR6007, 110 wpc;. SR7007, 125 wpc) supposedly being shipped in July. Would the power differences make any appreciable differences in the quality of sound for my Triton Two's? I listen primarily to classical music at medium volume in a medium-sized room. (I'm sure this sort of question has been answered numerous times in the forum, but my search didn't find them.)

The additional power (15-25w/ch) will make no difference on your Triton Twos. Usually there are other features (that may or may not be important to you) that justify the model jump, the power rating difference is likely not the main difference between these models.