A single 10" vs 4 x 18" high excursion subs???? Well, yeah, there will be a pretty dramatic difference!
If you don't mind the sound in the garage from the backwave, and don't see a problem with that sound infiltrating other areas of the house and causing problems, then I think IB is the way to go. A pair of those Fi drivers would provide enough output in that size room to keep most sane people happy.
As for what I think the question was, sure you could do both an IB and in-wall sub. Not much reason to except to have more than one sub location to smooth response, but a single 10 is going to have difficulty moving the needle much with 4 IB3 drivers or even just a pair.