I was looking at upgrading from stock speakers. I currently have a Alpine CDA-105 head unit. I wanted to upgrade the sound a bit for a reasonable price. Anyone have an opinion if I were to get the Alpine MRP-F300 amp and Infinity Reference 9633cf which are 6x9. I have a Chevy Blazer and I was planning on just getting two 6x9 speaker boxes instead of replacing the door speakers. Anyone have any opinions?