Can't be much wrong with the Impulse seeing as Strange have been kicking a$$ all year with them!
Unless you like carrying about 5 barrels around with you, you should really be using a Freak. Next thing to do is get hold of Smart Parts & ask them about all the tasty Voodoo goodies you can get - IMHO the Delrin bolt is a must & I think it's recommended that you change the hammer at the same time (something to do with weight, but I'm not techy enough to remember right now).
I'm sure someone else will post on here & suggest loads more bits & pieces as aftermarket add-ons for Impys seems to be a hobby with some of the guys!