warmer ?

What kind of preamp do you have?

gonna say the same thing preamp???

Demon DCD-510AE -> Straightwire Symphony 2 IC -> Musical Fidelity V-Can 1

I'm not sure what headphones you have, but assuming they sound OK, I would consider a new headphone amp. Since I haven't heard your system, understand that I'm just guessing. But that is where I would look first. Also, there are many headphone amps that have DAC's in them as well. You can get 2 upgrades in one box. Use the Denon as a transport.

any recommendation for one that does not need a warm up to sound good ?

"10-15-13: Ebfidelity
any recommendation for one that does not need a warm up to sound good ?"

Nope. Pretty much everything needs to warm up. It really shouldn't be something to consider, though. If its SS, just leave it on all the time. Tubes, maybe 15-30 min. for the average piece.