Should I add a separate amp?

Hey Guys,

I'm an audio novice but I'm setting up my home theater and wanted some advice. I recently purchased a denon 4308ci, def tech mythos st front three (wife wanted thin-I wanted good sound=compromise), def tech reference in ceiling rears (7.1) and JL F113 sub. My front towers both have built in subs but I'm wondering if right now, I would notice a big difference with a separate amp. Will the denon do the job? I think it's 140 watts x7 and I know the amp is usually not as good in integrated receivers. Will I notice a big difference with a cleaner, more powerful power supply? Thanks in advance-I'm lost.