Reason only creates beats and sounds, you need a DAW for advanced mixing and vocal recordings, etc.
The MBox Mini is prob a cool starter interface - but your buying PT LE along with it by purchasing the MBox so i assume that your planning on making PT your main Sequencing/Recording software then right?
As far as using the MBox mini soley as an interface and just avoiding the use of PT, to be honest im not quite sure what the status is on that? A couple friends of mine have the MBox but they always use ProTools with it since thats why they bought the MBox specifically. Ive never run into somebody that uses one to record into another DAW like LogicPro or something...
I would assume you can, but knowing ProTools i wouldnt be surprised if you can only use the interface with PT only, but hey who knows? Thats something u gotta find out I guess.
I would hit up Dreampolice, hes the goto guy being that he works at Sweetwater.