I'd recommend you stop calibrating by eye and try out a calibrator. They are increasingly cheap as digital photography progresses as proper calibtration is important. There are quite a few out there, I like the Gretag Macbeth (Eye One Display 2 is inexpensive if you only need to profile monitors). If you require a calibrated monitor because you are outputting (for professional use), then a calibtrator is a must (if accuracy is important). But if it is to increase the viewing experience, calibtrating to eye and buying the adapter you mention is probably a little cheaper.