I never compared my Scotty II to a K&N replacement filter, but I can give you my numbers with a similar setup to yours.
I also have a Comp and straight piped stock exhaust.
65-75 mph = 750-800* EGT with Comp on level 1 or 2
65-75 mph = 850-900* EGT with Comp off
Max EGT's with Comp on 2x5 = 1050*
Max EGT's with Comp on 5x5 = 1250*
I live in Houston, so all these figures are on level ground... mostly. We have no hills. Also, these figures are while running empty. I don't tow much, so I have no input there.
HTH. The Scotty II was worth the money to me, but for you, you'll have to decide...
Duane