The GA645 series is really the only thing that is in the price range (well, it is now) and does what the OP needs it to do. I'm not sure about -25 C, but I've definitely shot it to -18 C (0 F). The lens is as sharp as any 645 ever made, there is no bellows to go bad or front standard to get bent, and they run forever without maintenance.
People get so bent out of shape about automation, but it's nice to have an AE option and data imprinting. The AF and AE are pretty much perfect. The auto wind-on also makes it very quick to reload. In 500+ rolls, I've only fat-rolled one (because a paper 120 band hung on the takeup spool spring (and that could have happened with anything). It's also nice to have a small onboard flash for when you need a tiny bit of fill.
Uniquely, it's also the only 645 that you can operate completely one-handed or completely blotto on vodka, ouzo, grappa or arak.