I think your best bet would be to try to buy tix you want and resell the ones you do have.

If you look on ebay, there are tons listed. Keep an eye on the ones that are comparable to yours and you'll see how much you can expect for them. You certainly won't have any problems getting rid of floor seats.

I got my ticket at the presale for Seattle and couldn't get any decent pair - so I switched to single ticket and I got an ok seat.