Id expect most speakers with a 100 watt x 2 amp to get plenty loud for most people. After that you need to add a second set to distribute the power or not listen as loud. As for overpowering a lot is in the setup. I ran 200 watts to a side on my old alpines type x's only rated for 60 watts. I listen at resonable vol so the extra power was never a problem. It gave it a fuller sound. Crossover settings will also have a lot to do with the amount of power that can be handled. That being said when it comes to speakers everyone has their own opinion. I think ebay a set of alpine type x's for 200. They have an incredably flexable x over with some very well built speakers. Id bet you'd have to go all the way to the euro sports in the cdt line to find a better mid. I think even the tweeter in the euro set needs some work but that is just my opinion.