Sell them immediately ... to me ... for something absurdly low ... like, say, $200. Or just trade me straight-up for my black/polished-lip 10-hole monstrosities ... y'know, 'cause they're all, like, custom n' stuff.
Seriously, though, larger wheels tend to be heavier than the smaller OEM's. Far as I can see, 16" ponies seem to be about the optimal compromise between weight, looks, handling, and tire size selection. Unfortunately, everyone else seems to have the same idea about them, so it's near friggin' impossible, anymore, to find a nice set of 4 that isn't mutilated, missing caps, and/or way overpriced. Used ones are selling for almost as much as new reproduction rims, it seems...
Oh, and Cobra R's are done to death. Not that 16" ponies haven't been, as well, but at least they were factory stuff on some Foxes. Do you need the thinner-sidewall handling of 17's, or is it just a looks issue? If handling isn't a priority over traction, look into a set of nice Weld rims - pricey, mayhaps, but beautiful and light as a feather, comparitively.