In my estimation, if you have a DAC worth $500 used and $1,500 to spend, you are better off selling the DAC and getting a better dac with volume control if you have no need for switching through a preamp.
An asynchronous USB dac with volume control you would get better result in a computer audio only application. The obvious condidate would be the wired4sound dac2. Another option would be a PS audio perfectwave DAC with bridge as music server. I use this myself and recently did a shootout between DAC direct and running it through my $10K Modwright 36.5 LS/PS tube preamp and it was a very close call.
An asynchronous USB dac with volume control you would get better result in a computer audio only application. The obvious condidate would be the wired4sound dac2. Another option would be a PS audio perfectwave DAC with bridge as music server. I use this myself and recently did a shootout between DAC direct and running it through my $10K Modwright 36.5 LS/PS tube preamp and it was a very close call.