There are no less than SIX hotels in Marion, VA itself.

Google Maps is your friend.

Americas Best Value Inn $68 ($64.99 based on website) @ Exit 47
Econo Lodge $70 (Confirmed on website) @ Exit 47
General Francis Marion Hotel ($120+ on website)
Travel Inn ($45-47 phone in...but front desk clerk didn't inspire confidence) @ Exit 47
Royal Inn (downtown Marion)
Lorenzen's Motel (downtown Marion)

Personally, I think Americas Best would be the best choice with Econo Lodge as a #2 pick. Exit 47 is the nicer part of town with a gas station near the hotel, Mexican and Italian down the street, pizza, Wal Mart, Hospital. You can pull up on Google maps and see for yourself.

Wytheville, VA would have more options, but having done rallies out of Wytheville, I don't find it any better than what you'd find in Marion, AND more routes seem to be readily launchable from Marion. If you're going to superslab, do it when you want to get back to the hotel, not at the beginning of the ride.

This looks exciting!