2001 Ford Escape/SQ system

A 5X7 is the same as a 6X8.  But yeah, I agree with Rob, 6.5's for SQ.  You just can't get the same sound reproduction out of 5X7's.  Components would definitely be the way to go.  If you can get them to fit in the doors, then yes, I'd just put the tweeter where the factory one was.  If you think fitment maybe an issue (a good possibility with deep angled baskets/large magnets found in quality speakers), you maybe able to construct some kickpanel enclosures, and you can put the tweeters there as well.

For your headunit I would defiantly go for an Eclipse http://www.eclipse-web.com their headunits give you unparallel sound quality. For your mids and highs my first choice would be MB Quart, and Focal. I would also look at Eclipse and Diamond Audio as well. I would also suggest that you go with 6.5’s. As far as amps go if you’re looking for a good sq I would suggest Diamond Audio as my first choice or Eclipse. For the lows look at MB Quart or Focal and if you want SQ that will bump hard look at the Eclipse Aluminums.

You will need to make a mounting adaptor, thus this adds a little space for a larger driver, if you center the midbass driver on this adaptor, you may be a ble to squeeze in a oversize 6.5" mid. Take your 5x7" out, turn it upside down on a piece of 1/4" cardboard and trace the outline of the speaker onto it as well as the speaker mounting holes, cut out the shape. This is your template for whatever speaker you may want to fit it. Find yourself a set of speakers that you like and trace the mounting cutout of the mid onto the center of this template and cut out the center. Test fit the mid. Test mount the cardboard template onto the door, you may have to cut a little metal depending on the speakers, this is an easy task to do, trace it out with a black felt pen.

Now by the sounds of things this is a lease vehicle, If you are only cutting out slivers of metal, which I expect is what you may have to do to get the sound you want, there is nothing wrong with this. As long as the factory speaker can still mount (and it should easily), the door panel is not cut up, the chances are that the dealer will never ever look behind the door panel for cut metal, it  is just not worth their time. Once you have a good fit on the template, trace it out onto mdf (resin & paint black the mdf when complete). You should be on the way for decent sound.

For an idea on what an oversize 6.5" mid is, have a look at any MB Quart component speaker compared most mid fi guys like Pioneer or Kenwood, you'll see a drastic size difference.