I've got a 2M blue (ca £100) and think it's excellent. The stylus of the OM20 will be better than that on the 2M Red, but roughly equal to the 2M blue - I wouldn't go for the red as it could be a backwards step.
Basically, the 2M range are all the same body, and it's the type of stylus that determines which "colour" it is - Red has a standard elliptical, Blue a nude elliptical etc...
The 2Ms have a slightly forward sound compared with the OMs and the Goldrings, while the AT is similar to the 2Ms and has almost legendary tracking abilities...
I would either go for a replacement OM, or push the boat to a 2M blue... the 2Ms look much more "gucci" as well!!!