I am looking to replace the 5.25" door speakers and add 6.5" speakers to the back. I'll need to make the rear enclosure so that size is flexible, but the 6.25" seem like a good fit. These will be off of a Sony CDXGT700HD. I'm not wanting to spend more than $100. total for both pair. Yes, I know that is cheap. I'm simply wanting to make a significant improvement from the pair of $10. factory speakers in the doors. Any suggestions? Thanks in advance!