I too bought the Mamiya 645E because of a shortage of American pesos, and have not regretted it. For a brand new camera package you get a lot for your money, and the Mamiya lenses are sharp and contrasty and always give excellent images to work with. The only downside for me is that I now find myself doing more portrature than I was doing when I made my purchase, and find that because of the rectangle format I am always turning the camera on its side which makes it a little ergonomically clumsy. So you have to consider that if you are a people photographer. If I knew then what I know now I might have saved up a bit more money and gotten a square format MF SLR.
I also have a small collection of TLRs and would recommend you at least entertain the idea of a used Rolleiflex, Mamiya C220-330, Minolta Autocord (our own Les McLean says he spent the first portion of his photographic career using the Minolta, and he has some wonderful pictures to show for it). The twin lens cameras can be had for even less than the new Mamiya kit, produce terrific results, have totally mechanical operation so you won't be left with a suddenly dead battery and an unworking shutter. With a little homework and patient hunting you can find used TLRs in practically brand new condition, and still have some money left to get the things you need to start your home darkroom. There's no going back now...