Biggest concern is installation. Drivers matter hardly at all in comparison.
You are also being very confused by marketing. Power handling has NOTHING to do with output. No matter what you choose more output will be directly proportional to less frequency response. Everything is a trade off.
Slapping the XXX set in your installation as it is now will have WAY LESS of an effect as fixing the install. Your drivers may not be good, but there is nothing special about the set you are looking at either.
As for adding an 8" driver with a comp set, that isn't logical at all either. If you have an 8" midbass then the mid on the comp set should be WAY smaller. A 3 way set with an 8, 6.5, and a tweet is down right a serious waste of money.