Do it. That’s a great deal, and if you end up needing the +Drive, you can either send it in for an upgrade, or easily resell it. You will love it, I promise!
Not having the +Drive doesn’t mean the sfx60 isn’t still a beast. After owning a sfx60+ for about five months now, I can say that the ability to load user waves is not a ‘make it or break it’ feature. The extra working space of the +Drive is nice, but not that important unless you’re playing big live sets all the time.