Yes, wire upgrade is a must! You have to buy a nice amp kit, or have the stereo shop personalize the proper setup for You.
Big 3 is also a must! (great advice - as lot of people skip this!)
And make sure Your alternator is able to support all Your electrical needs. With a bigger system, an alternator upgrade is highly recommended.
Lot of people buy a cap, and believe, that it will solve their problem. Don't be fooled. If You alternator is not strong enough, it will not be able charge Your cap, so basically, it is useless.
Have good power and ground wires, RCA's and the BIG 3!!!
And don't cheap out, do it ONCE do it RIGHT.
I know a great shop if need to be...one of the best in TO.