2004 F150 stereo installation

I will be collecting my new F150 Supercab from Liverpool docks in the UK in a couple of weeks but I'm eager to have all the audio kit ready to install as soon as it arrives. I'm therefore wondering if someone can help me out with a few questions:

Does the 2004 F150 take 5x7 speakers in both the front and rear doors? Is there a good space to put a component tweeter in the front doors? I was hoping to use JL Audio XR570-CSi components in the front and XR570-CXi coaxials in the rear.

Is there a useful place to hide an amp away? I have a 4 channel Sony amp that I'd like to use but it's quite large. I may well buy something smaller and better if I it turns out to be difficult finding a space for the Sony.

Ultimately I plan to have a PC in the truck but that will have to wait until the new Xenarc fully motorized, in-dash 7” touchscreen VGA monitor is finally released later this year: http://www.xenarc.com/news/news-011904.html Meanwhile I will fit a regular single-DIN head unit. Has anyone tried to fit two single-DIN head units into one Double-DIN mounting hole? I'll need to be able to do this to have both the Audio controller and the PC screen mounted in the dash simultaneously.

Many thanks  

I guess that the 6x8/5x7 specification of some speakers means that they're actually 5x7s but supplied with a mounting plate to allow them to fit 6x8 holes? I wonder whether I'd be better off finding some 6x8s to fit rather than compromising by using 5x7s Do you have any suggestions - bearing in mind that I like the sound of the JL Audio units?

From your reply I guess that there are no good spaces to fit tweeters - under the door grilles.

Do you know where the factory 'audiophile' amp is usually mounted? I thought that might make a good mounting location but maybe theire 'premium' amp is rather small!

Thanks for your help.