I have communicated with them in the past (to try and consign), they are one of the few places that have a physical store in Texas and I was thinking of consigning some John Wayne posters to them, but we couldn't agree terms.
They are expensive but I believe them to be legit and if the price was right I would buy from them, that said and looking at their prices it is unlikely I will ever do business there.
I am curious as to what 'title' you were looking for (if you want to share), as it is unusual to find a given poster from one source.