Well IMR800X is what Underwood uses in his loads!
The SPP are used in NT - "non-toxic" primer situations. I have used them with good results. Many people don't like having mixed primered brass especially those using progressive presses and getting them mixed up!
You could drop by here http://10mm-firearms.com/index.php
as I have posted the pull-downs of the 10mm factory ammo.
Great bunch of guys there too! Best regards!