Jim,
Before getting any new toys just buy a roll of 120 film and come over. I have a Yashicamat 124G that you can try for a trial of medium format.
In focal length terms the standard lens on full frame 35mm is 50mm. On 6 x 4.5 it is 75mm and on 6 x 6 it is 80mm. Up to now you have been playing quite a bit wider so that may affect your style.
Don