Honestly, if all you're trying to do is do better than the DAC in the Touch, that isn't going to be very hard to do. As I mentioned, I'm running a very modest XDA-1 DAC and it is a clear improvement over the internal DAC of the Touch.
There are lots of DACs out there and many of them sound good, albeit different.
What I'd do is pick up a used PS Audio DL III. It's a nice DAC and goes for around $400, used.
I'd also like to make a comment about equipment with tubes. If you decide to go with tubes, be prepared because it is a bottomless pitt. I'm just dipping my toes in the tube pool and am finding that good tubes start at about $100 a pair and go UP from there.
There are lots of DACs out there and many of them sound good, albeit different.
What I'd do is pick up a used PS Audio DL III. It's a nice DAC and goes for around $400, used.
I'd also like to make a comment about equipment with tubes. If you decide to go with tubes, be prepared because it is a bottomless pitt. I'm just dipping my toes in the tube pool and am finding that good tubes start at about $100 a pair and go UP from there.