I found Universal Piano Services in my online search for used piano warehouses in the GTA. Several websites had given them great reviews and I was both optimistic and apprehensive at first, but was definitely not disappointed with the experience! I called and spoke with Ilya, the owner, and we set up an appointment really quickly and Ilya was very accommodating of the time request. The place is a warehouse with a small office and besides the technicians who do the restoration and refurbishing of pianos, Ilya is essentially the only one to show you around, hence the need for an appointment. Ilya was great and very personable. He's very knowledgeable on pianos in general and knows his stock very well. He knew exactly which ones to show us when I described what we were looking for.
The warehouse carries both a good selection of uprights and grands. Ilya also partakes in the design and process of the pianos refurbished. I thoroughly enjoyed my experience there. It was professional, efficient, and expedient (I was in and out with a piano purchased in under an hour :)). The prices were very good and a long warranty is included, plus free delivery and tuning with the purchase - you can't beat that. I would definitely come back if I were to purchase another piano and have recommended this place to some friends already!