Thank you so much guys for the excellant info.. You all have got me more confused.. I guess I am gonna have 1K + budgte after selling my M2 in excellant condition and the 40mm lens..

So it looks like between the mamiya and the pentax.
The pentax system looks great inspite of no interchangeable backs. But does the 645N has mirror lock up function?Th elenses, as I hear , are some of the best in the industry and also we can use 67 lenses which essentially means we are using the sweetest spot on the smaller negatives.

The mamiya will have the advantage of inderchangeable backs (I am not concerned) and the superb lenses with 80 f1.9 being the dream and pretty cheap..

Its confusing!!!!