Recipe probably uses Summit to keep hop mass and cost down. If you want to use American hops, look to the noble daughters (esp. Mt. Hood), not grapefruity C-hops, unless you're going for the Houblon Chouffe IPA Tripel thing.
I'm really happy with my recent Tripel with 100% American hops (Mt. Hood and Willamette).
Keg: Simple AIPA (2-row, Chinook, Cascade, WLP090)