Test: Comparing an AV DAC sound to a Pre-amp

I have a Proceed AVP (driven by a Theta Dreadnaught and Aerial 10T's) and a Meridian 508.20 DCP with the 24 bit upgrade. I'm wondering this: Would a preamp such as a Levinson or Rowland be a major improvement in sound warmth over the analog AVP connection I use now?

I'm looking not just for comparisons to those two pre amps, but any suitable preamp comparisons. I guess the question assumes that someone has at least heard the AVP long enough to know its sound. (If it matters, I use Audience and Cardas GR IC's and Audience speaker cables.)

I appreciate any experience you can provide. I like the Proceed sound on 2 chanel, even without a pass through. Yet I can't help but believe that a major improvement is in store just the same. Thanks, Joe