Here's a whacky idea, but not much to lose at this point I guess. Maybe you can round up some other 5.3 owners who need and/or want backup drivers and you can pool together to purchase a pair of 5.3s and split up the drivers? So if you could find a decent used pair for $600 or so and two other people interested in drivers you could spend around $200 each and have at least one midwoof and potentially a tweeter backup as well. Not optimal to be sure, but still cheaper than buying another pair of speakers and you'd get to keep enjoying your 5.3s.
Anyway, as a 6.2 owner I feel your pain, and best of luck.
Anyway, as a 6.2 owner I feel your pain, and best of luck.