@kds my immediate thought was that a tube preamp would sound better, but you have a really nice dac, so I don't know.
I'm using a Linear Tube Audio MicroZOTL preamp (level 2) with a Coda 8 amp. It's much better than using my dac as a volume control, but your dac is much higher end than mine.
If you can purchase a preamp with a return policy, I think I'd give it a try.