Theo, Beethoven's Waldstein sonata is my favorite of the 32 sonatas he wrote. Also, it is a great piece for equipment audition. Very dynamic and engaging. You can listen to it 1000 times and not tire of it, which can be helpful when you are auditioning equipment.
I like to use good recordings of recent vintage for auditions. The Schiff account on ECM of this sonata is a pretty decent recording. Not sure if he used a Steinway or Bosendorfer grand for the Walstein. The Paul Lewis recording of this sonata is also probably very good, but I haven't heard it yet.