2 speakers or 4 with a sub? plus other ?

Here is my current setup, in my Ford Ranger Supercab.

Sony CDX-F7700 headunit

Kenwood 2 way 6x8's in the front doors

Kicker Solobaric 8"L7 2ohm dualvoicecoil in a rear firing custom built sealed center console approx .6 ftcubed

Kenwood 7202 2 channel amp, bridged to output 460rms/920peak (4 gauge power/ground)

My question is, the rear speakers are about 3 feet from the front ones and are the stock Ford speakers.  At the moment I do not have them connected, just the front 2 Kenwoods with the Fade to the front.  Good idea or bad?  I figure the stockers will sound like poo compared to the Kenwoods.  Am I wrong in assuming this is also easier for the headunit to output more wattage to just the front 2 instead of 4 speakers?  I think the sub would sort of drown out the rears and being so close to the front doesn't seem to lend well to a front and back soundstage.

Without buying new speakers, should I A.) Leave only the front 2 connected  B.) Connect all 4

If I do not connect the rears should I install them anyway (thinking slight sound dampening from speaker filling the hole instead of a hole with the sheetmetal on the other side?

Will adding non-Ford 6x8's in the rear powered off the headunit really be worth it?

My eventual plans are components in the front, Kenwood 6x8's moved to the rear and both sets powered by an amp that matches the speaker requirements.

Final question, is there a proper way to adjust input sensitivity on my amp or is it just personal preference?

Leave the $1.99 OEM speakers disconnected, and it doesn't matter whether you take them out now or later.  Might as well take them out when you have something to replace them with.  Move with the quckness to your eventual plans.

Forum search for setting gains

• https://www.the12volt.com/installbay/forum_posts.asp?tid=71427&KW=gain 
• https://www.the12volt.com/installbay/forum_posts.asp?tid=69172&KW=gain
• https://www.the12volt.com/installbay/forum_posts.asp?tid=63813&KW=gain
• https://www.the12volt.com/installbay/forum_posts.asp?tid=62247&KW=gain
• https://www.the12volt.com/installbay/forum_posts.asp?tid=61468&KW=gain

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.