Aside from the obvious: Most likely a lower price home, lower mortgage payment, ability to pay cash for home etc... There are many less obvious monetary benefits from making the switch.
1. LESS CLUTTER! You will lose much of the space that was previously used as "fill-space" no need to search for that decorative couch that no one sits on, or that grand piano that no one plays. Space will be used much more efficiently, thus saving money.
2. LOWER UTILITIES! No need to heat the room for guests who no longer have the opportunity to sit on the unused decorative couch.
3. GIVE LESS TO UNCE SAM! With all else being equal, most likely a lower price home will result in lower taxes.
4. MAKE MONEY! What do you do with the your collection of couches, your accumulatin of lamps and enough plates to have the Colts over for Thanksgiving? There are a few opprotunities to make money getting rid of your no unused things. A garage sale is the hard way... there are consignment stores for almost anything you can think of! Save time, make money, and get rid of stuff; take your couches to a furniture consignement store, your old clothes to Plato's Closet, and your many bikes to Play-it-Again Sports.
What will i do will all of this extra money!? The opprotunities are endless!