Gonna add another vouch for Wolfgang as well, definitely the most honest dealer I've dealt with, price-wise and otherwise. He even found a poster for me and from what I can tell he didn't make much or even anything personally off the sale, which certainly made me a repeat customer.
Oh and I have nothing but good things to say about our very own Matt(marqueeposter.com), he's always top notch and honest. He's always given me fair prices and worked with me if I needed to negotiate the price a little. Also his detailed condition notes are accurate and his photography is great, what he describes is what you'll get. He's also very knowledgeable.