I initially used a Sound Science Diamond Music Vault server with my DA-06 and had excellent sound... but when my server starting having hard-drive problems (age related), I tried replacing it with the PS Perfectwave Transport (in large part because of the good reviews on Audiogon), but came away feeling the music was flat and lifeless. I also tried an older CEC transport, and while it bettered the PS Memory player, it still fell short of the sound quality from my Sound Science computer server. The Bluesound Vault 2 I have now is not as good as the Sound Science Server, but It's better sounding than the CEC and PS audio transports by a fair margin and provides greater flexibility at a great price. My best digital source is a Audio
Aero Reference CDP, but it's very pricey and the company sadly went belly-up in 2012.
If you do want to try a PS Audio Memory player, make sure you get one from a reseller with a good return policy (The Music Room / TMR) in case you don't like it.
While I have not tried the Jays Audio Transport recommended by Twoleftears, I have heard great things about it and would give it a try if the dealer has a return policy.
BTW, I greatly respect the opinions of Charles1dad and Grannyring, as they are both generous, long time, reputable contributors to Audiogon.