If you buy from a dealer, you should be able to negotiate a price which includes tax, bench, delivery, and a visit to your home from an experienced technician to tune and voice the piano to your satisfaction.
$15-20k should buy you a really nice piano, whether you decide to buy new or used!I would stay away from the cheaper Yamaha grands. Yamaha is not an inexpensive brand. If you are looking to buy an inexpensive grand, there are many good manufactures which specialize in this segment of the market, and you would do well to consider them. For 20k on the private market, you should be able to get one of the 6-foot Japanese instruments, either an RX3 or a C3, 10-15 years old with fairly low-mileage, from the original owner. If you go to a used piano dealer, the same money will get you an RX3 or a C3 that is more like 25-30 years old, but the price will include delivery and a warranty. Mason and Hamlin is a well-respected American firm that has been building high-quality instruments for a very long time. They never developed the market visibility of Steinway and Sons, but many pianists and piano technicians consider their quality level to be similar.
I think I would start by going back and checking out that Mason and Hamlin a little closer since you had a good feeling with it. It's a very good brand.
My favorite piano in college was a Mason and Hamlin. I have a wonderful piano that my neighborhood dealer helped me find, but if I were to be back in the market, they're the first brand I'd look for.If you're looking the C2-C3, have you considered the Avant-grand digital? An Avantgrand costs about half as much as a comparable grand, fits in the space of an upright, has a real grand piano action, and you can practice with headphones...
Great suggestion. Already forgot age and price of that one but I found the sound just gorgeous. Will have to go back on day off without wife and kid :-p