You need to weigh up the options. As you already have the 645 I'd question getting a C330, I had two C3 series Mamiya's great cameras and lenses but when most of the system was stolen I opted for a 645.

Now 30 years later I still have the 645's which get a little use however I now use a Yashica 124 (when in Turkey) and a Rolleiflex 3.5E (in the UK) and they are more fun to use. The quality from both these TLR's is excellent and I'm producing exhibition prints that will sit alongside those made with my 5x4 and 10x8 cameras.

Ian