For something of this size I recommend your local Craigslist !! That way they will pick up and no shipping is involved !! I have had good results there on large items but none were antiques !! Have sold Horse trailers, boats, barges, and motor homes !!
But if you use Craigslist,,be sure someone is there with you when its picked up !! There are too many nuts in this world !! And do not fall for the scammers,, there will be some !! If you are unsure about something or someone who offers you an unbelievable deal,, please ask here before doing anything !! I am usually here daily !! And never give your address until you know they are interested !! Just give the town name and your first name !! You can tell the scammers by the questions they ask !! Most know nothing about what they are asking about !! I listed a cutting horse once and they asked me if he came with a cage and didn`t even want to see it or know anything about a 1000lb horse !! That would have been a very large cage !! The people who are the good buyers will know about antique and vintage furniture !! You might even do well with just an ad in your local newspaper !!
Be sure to tell whoever buys this sideboard not to refinish it !! Pretty sure much is faux grained and the graining will be removed if they do !! You do not find that much faux grained furniture anymore in as good a condition as yours. Everyone tries to refinish them and the art has been lost !!
I would love to have something like that to use for a bar !!