I haven't seen a case or box for either set on eBay in quite a while. You could try Buy-It-Now listings for the cases for a week or run seven-day auctions and see what happens. You won't be out much money if they don't sell and depending on your BIN price or starting bid, you could receive a good offer. There may very well be people who missed out when the sets were released and would be willing to pay for an entire case. If it doesn't sell, then you can try one box at a time, preferrably one from each set per week.
I would definitely list the cases/boxes for both sets at the same time. There could be one of those crazy bidders who just has to have both.

The tricky part is determining the price or opening bid. Thinking way back, I think the prices for POA eventually settled somewhere around $125 to $150 per box. I'm not sure about COS.