If cost is not important, just buy the 5400 and arrange auditions with dealers for the Meridian and EMM so you can listen to them in your own system. You won't lose much on the 5400 in resale, and can determine which of the three suits you best. I have the 5400 and listen to a lot of jazz piano. It's very good. haven't heard the EMM or Meridian, but would be shocked if you didn't find either of them, or the PD, was better than the 5400. If I were spending almost $20,000 on a digital source, I would insist on hearing it in my system before writing a check. Forums and reviews are great, and you'll learn a lot about other people's preferences, but you really need to hear them yourself in your own system if you're going to spend significant coin.
