What exactly do you mean by "crossed from 100 to 750 for the rear"? Also I did buy some coaxials for the rear but they sound like crap. I think they may be blown, I do not know. There is a rattle sound coming from them when there is some bass in a song. They didn't do that to begin with when I first got them. If they did, it was just barely. Now its hard to get them to NOT rattle. They are only 60 watts though, and that amp I linked is 336 watts RMS which means 84 watts per channel.
So it looks like I overpowered the coaxials by about 24 watts. Probly killed them.
I personaly like rear fill if you time alignment. Delaying them is always dun for a deaper affect.
Stinger 0 600 Hz Bass Blockers Car Speakers SGJ92 | eBay
these will help from blowing the speakers next time,if they are 6.5 speakers..They make some for the 5.25/ect.Placed on the + connection to the speaker,and keep the gain down low will be just fine.Sounds like you Blew those speakers.
It seems I screwed up using 60 watt speakers on that amp. I guess I should have had the gain set at zero the whole time. I did turn it to zero after the fact, but by then it was too late. Live and learn I guess.