Franklin,
The SB250s are only 19" deep. So if they're standing upright side by side in the van, it'd leave me more room for the other gear. I really like how my current subs sound, so I'd be reluctant to do away with them. I think eventually, a trailer will be on the list of things to buy...
Sounds like a plan. I don't know if you have tried yet but you might want to look into optimizing your truck pack. The order in which they go into the van and where in the van you put them might give you the needed room.
Good luck. Also, I can't tell by the pics but if you don't have grills on the subs, you should.