Hey there, I'm in the middle in of massive overhall of my Stereo System. I did buy the JL 300X4 today. My goal is to replace the whole back pannel with a fiberglass enclosure. NO SMALL TASK! I'm not sure if you have taken off your back panel. If not you will discover that the JL 300 will not fit right. It's not as easy as you might want it to be. The Amp will be perfect to run the whole system. Buy a component system and you will cover your doors and the tweeters. Many agree throughout the forum that you do not need your rear speakers. Do away with your Monsoon Amp all together (my oponion). You can you bridge the Amp to 150 watts and cut it over wherever for your Sub. I'm using a JL 10W1 I have about half of the work done. I'm using a JL Clean Sweap straight from the head unit. It has Aux in also so I might make a custom holder for an IPOD or Zune. Propable Zune so I can have FM and basically used that and not the head unit. I ordered JL 6 1-2 Coponents for $299 off of Crutchfield. I'll keep you posted.
This is the first time I will attempt to install everything by myself, also this is the first time I'm using fiberglass. So far so good.