Ortofon 2M series

Anyone have an opinion on this series of cartridges? I'm about to make my first big cartridge upgrade (I purchased a Pro-ject Debut II three years ago and moved up from the stock Ortofon to a Grado Green about two years ago - I also have a NAD PP-1 preamp) and I was interested in spending $200-300 on a cartridge. Obviously I've been looking at the usual MM/HOMC suspects (Grado, Sumiko, etc.) but I still haven't gotten the acrylic platter upgrade for the Debut, so I'd have to do that before buying a MC cartridge.

Anyways, after all that long-winded explanation, any thoughts on the 2M series? I know the Black is a significant upgrade from the others, but how do the lower models differ from cart to cart?
I suppose my main question is how far above the rest of the 2M series is the Black...all the reviews I've seen so far seem to think that the upgraded stylus puts it in another league.