My main advice, other than make sure you buy an acoustic, is don't rule out second hand pianos. You can get some well maintained, older pianos which are of far better quality than you might expect, especially with regards to sound. I have a gem which was bought new for close to £10k but never used. I think we picked it up for about £1800 because the owners had it in storage and just wanted to get rid of it. Also, before buying any piano, make you sure you get a trusted piano tuner to have a look at it and make sure there are no problems with it.