Thanks for the replies.

Yep, I emailed DP and Justin replied that they won't sell tunes to run on Hydra.

Summaries so far as I can tell:

PHP is significantly less money for the package with more tunes - but I don't want most of them. People report difficulty getting support, and their own web site warns of it being hard to get a hold of them.

DP is more money for the package with the five tunes I do want, but Justin promptly answers questions - usually the same day.

I want the best tunes and am willing to pay for them, but "best" is hard to tell from behind a keyboard.