ruffo76
Hello & Welcome to the Forum!

Choo Choo Auctions, Lionel Rolling Stock Price Guide.
http://www.traincity.com/price_guide/pllirsp.html
Your 6456 Hopper, Glossy Red w/Yellow Letters in Very Good Condition is listed at $85.00.

AmbroseBauer Trains Auctions
http://www.ambrosebauer.com/auctionlist.php?auction=143
Your 6562-50 Black NYC Gondola w/cannisters, original box, is listed as lot # 13, selling for $15.00
(which is the same price I received for the one I sold.)

In general, PW locomotives and rolling stock prices are down from what they were a few years ago when prices were at their peak, unless it is a rare item.   You may get the price listed  for your 6456,  or it may sell for more if more than one person is seeking that specific car for their collection and get in a bidding war.  It may sell for less if no one is looking for that specific car.
If it's being auctioned, it's subject to the whims of the buyers.

Good luck with your auction, if they don't sell, you can always list them here on the forum in our Classified's sub-forum and avoid the auction site fee's.

Happy Rails.
Dave