As you probably know, using the DAC improves the sound of the BCD player, so it's worth using it for that purpose alone. I have the same DAC and CD player as you, and plan someday to get a BDP. When I do, I will buy the latest Bryston DAC and use my old DAC on my second smaller stereo system, assuming it improves the sound of any CD player connected to it. I personally would find it hard to accept a $1,000 loss for two years of use.
If you don't need the money, I vote you keep it. Stereo equipment is a bit like cars. They depreciate the most at the beginning and level off as they get older. I must confess, however, I own several pieces of equipment I no longer use, but can't bear to sell for pennies on the dollar.