So I've got some front components & rear coaxs for my MS3 Sport. I've got an MTX REQ-5 for the sub... The guy that's doing the install recommended I get another amp to power the speakers... saying that the factory HU is too underpowered. I wasn't really intending on breaking the bank for this but obviously will go for it if it's truly necessary. (he said at best I'd have to crank it up REALLY loud to hear anything and at worst it would sound like s***.) The cost of a 4 channel amp combined with the install will come out to at least $300. The fact that I'm sticking with the factory HU should tell you I'm not some audiophile freak. So what do you think? Should I plunk down the dough or just hope it works well enough off the factory HU?