I am happy with my 135 kit, now I need to complete my 120 kit

I am happy to print 10x15cm on 13x18cm paper from 35mm. Before a long time user of 20x25cm(8x10") paper to print 35mm, big size prints are good but I felt a nice balance in small prints.

So 645 is redundant for me.

My enlargements are usually 11x14. I have done it with 35mm on a few shots. While it worked, there was some loss in sharpness from the original. Since I do a decent amount of shooting at car shows and museums, 645 will allow me to enlarge a bit more.

My folder is an Ercona. It is zone focus and a fantastic camera for easy walking around shots with a general distance dialed in. A 645 SLR is just going to be a little bit easier to dial in DOF.

Good luck. I wish you make lots of prints.

I have a Fuji GW690 which I doubt fulfills the criteria. Depending on who, it is light or not, bulky but good results. Older models can be found for your budget, especially from Japan.
Seeing the discussion around 6x6, sometimes I have thought about having a 6x6 camera. The orientation and film economy aspect, sometimes 8 frames are too few.