Definately the way to go is the Altrak from Trutrak since you're already flying with the wing leveler.
Works well with your Digitrak (you can hook them together if you want). Just a note, I had mine wired together but they're wired together you have to use the AP's together, and I preferred to be able to use them separately, so I cut that wire.
Just added one to my RV6 about 2 months ago....it's GREAT!
Overall, you'll be REALLY happy you did it. Just an FYI, but if/when you're running the wiring or harness, make sure to run the extra wires for the soon to be released "VS" (vertical speed) addition to the Altrak.
Contact me off list for details or any questions.
Cheers,
Stein.