Hi Mike,
I would surely go for the tungsten piston as well. If you have to hammer in bezel settings or heavy channels the Lindsay makes a nice hammer tool with the tungsten piston and the foot control. I do have a Badeco Hammer piece wich works on my flexyshaft and that one is more powerfull but doesn't engrave.
The regulators are perfectly matched for the Lindsay airgravers but I am sure that other ones would do if you can get the connection right.
I had the same questions about a year ago. The answers given too me from the experts where, Go For It, You Wont Regret It!!! And until this day I have only one regret. I should have ordered it long ago!!
If you want to know,
http://www.handengravingforum.com/showthread.php?t=1375
Good luck with your choice!
Daniel