Welcome to the Forum, Nate!
I evaluated that sub a couple of years ago, comparing it to a few others in its price range (see it here). I can’t speak to the HSU, but I imagine dollar-for-dollar anything you can get from them for the same price as the VRP should be a better sub, due to the retail mark-up of the latter. Spending $300 more with HSU will surly get you a sub that will blow away that particular Velo.
Your room is about half the size of the one I evaluated the VRP in. With equalization you should be able to get extension pretty close to 25 Hz. Check our REW and BFD Forums for more info on that.
Regards,
Wayne