from what I can tell, the 4.5 has the tweeter and can take 100 watts more power. it also weighs 40 pounds more and is a few hundred dollars more. is it worth the cost to get the 4.5 instead? how much louder will 100 watts be? if i get the TP then i will get the 3500 amp to go with it, giving me 240 watts. for the 4.5 i will be getting the 5000 amp. i will be taking this to school and be playing gigs with it, so weight is an issue, but better/louder sound is more important. so is it worth the extra cost for the 4.5?