tweeter placement

I have a 2005 Honda Accord DX.  My car has spots for tweeters in the top corners of the dash and woofers in the door.  I had a pair of 6.5 Infinity reference coaxials running off an amp.  I am using the factory radio which only has bass and treble controls.  Anyway, this system sounded alright but I had a pair of MTX Thunder 6.6 convertables that I wanted to put in.  These have a 6.75 woofer and tweeter that can be mounted as components or coaxial.  I put them in as components and the tweeters are so overpowering it's ridiculous.  My questions are:

1. Is this because my factory radio is so basic?  The infinities didn't sound that bad.

2. Is it just bad tweeter placement, would coaxial be the best way to go because the drivers are just too hfar apart.

Also, the crossovers have no attenuation jumper, they're pretty basic

Any help or suggestions on how to deal with this problem would be appreciated.

Update,

A friend of mine wanted to take a look at my setup before I went through all the trouble of moving the tweeters, and this is what we came up with. For the front and rear channels my amp has 2 settings; full range and high pass which has a cutoff of 85Hz. I had it set to high pass.  My seps however can handle frequencies down to 55Hz. With that being said I had no frequencies between 55 and 85 Hz. We now have the amp set with fron and rear to full range. The rear is a pair of 6x9's, and the front is using the include crossovers to filter below 55 hz. because of this the soundstage improved and the tweets don't sound as overpowering. I very happy with it. I'm still testing out varous music sources just to make sure, but I think it will work. I was wobndering though as to why the system did sound better with just the flick of a switch.