tube dac for tube amp?

hi, is it a better match to purchase a tube dac if using a tube amp?
Not really. Analog (especially tube) designers are not usually the greatest digital designers. The converse is also true.
A 'tube' dac? That is an oxymoron. The sound will always be 'digital'. Better to look for a good DAC and skip the tube part.
There is no straightforward answer.

It's a personal decision that depends on a lot of things.

What matters in the end is how everything gels towards the end of delivering sound in a manner that meets your expectations.

In general, I would expect the utility of a tube dac to be less for most that also use a tube amp compared to those that do not.

In my own experience I`d say what affects DAC sound quaility the most is the the implementation of a very good discrete analog section and a potent well designed power supply, more so than tube or SS. It also seems this influences the ultimate performance more than the type of digital chip selected.