Mr. X,
I have gone both ways First with Sorels, then to plastics about 8 years ago, then back to Sorels for 5 years and now back to plastics.
The real question is do you plan to camp overnight outside in the winter?
If so, then I would definitely Follow Dr. Wu's advice and get sorels, the cheaper alternative to being able to take the liners out and keep them from freezing.
My sorels do fit my Grivel G-10's with no problems and the G-10's fit much better than my old strap-on crampons.
If you are not camping out overnight, then I think the Columbia Bugabboos or Titaniums (which I also own) will do just fine and set you back about $79 and easily fit your snowshoes or crampons. Just make sure that whatever you buy has a lip to hold the snowshoe strap in the back.
There is also ebay for used plastic boots, but you really need to try them on in a store to get an idea of fit. But what the heck, if they don;t fit, put'em right back on Ebay.
SapBlatt, I really like the Conquests, but I had a really hard time getting my foot in the boot as the tongue is connected all the way to the top (Like trying to put your foot into toilet paper roll
) I figured if I struggled that much in the store trying to get them on, imagine sitting in a tent vesty at 5 degrees out and struggling with frozen fingers!!
(PS You must make sure you have the newer G-10's, becuase the older model had a nut in the back that would just scratch away at the back of the heel of your boot, eventually wearing the material thin)