I had a TriVista 21 DAC too, and also thought about having it modded. UnderwoodWally brought up two good points to think about before doing this:
1. You will not get the price of the mod back upon resale.
2. If you don't plan on keeping the DAC for a long time, keep the $1000.00 and put it towards the new DAC.
There are much better DACs out there, but of course they also cost more. So, what's your goal for your system?
Chuck