I'm trying to understand what you're asking for (can you turn off caps please?)

You want to run the 2 rear speakers and add 2 c-pillar speakers, right? What are you powering them with? Even the best of aftermarket HU's usually put out around 20-25W RMS per channel, not enough to power a set of speakers, let alone 4. Your best bet would be to get four 2ohm speakers and wire them so your right rear and right c-pillar would present a 4ohm load, do the same for your left side and then your fader and balance controls will still be somewhat functional. You need an amp... or two 

I believe the stock Pioneer unit was rated at 12W RMS or so? Just not enough... Even my setup will be underpowered and I'm feeding them 50W RMS each and sub will be getting 450W RMS. Look at amps from reputable companies, you'll see the average is 50x4 and for good reason, speakers need wattage, especially low to mid level speakers running on passive crossovers, the xovers just waste a lot of power as heat 

No such thing as an ignorant Q man, you ask it and people should be glad they can help you. I hate arrogant people that make others feel like they shouldn't ask questions... ok, off my soapbox lol

Yes, there are multi channel amps. I myself was looking at this one, it might be good for you: JBL GTO 755.6 it's a 6 channel amp
http://www.jbl.com/car/products/product_detail.aspx?prod=GTO755.6&CheckProduct=Y

I decided against it due to size. I wanted an amp that could fit under my passenger seat, so I got less power, but easier to stealth install. My amp: Eclipse XA5000 it's a 5 channel amp. Shop around, crutchfield is a decent site to pick up some basic knowledge, reading is your friend. I hang out on ICIX http://www.icixsound.com and am trying to relearn a lot of stuff, I used to be into car audio years ago but now am lacking a bit, have to pick it back up.

Plan your system ahead. My considerations were budget and stealth, demanded NAV, use of my XM Inno and a decent sub stage. I knew with Polks and only 50W RMS per channel I wasn't going to get amazing sound, so I set my expectations accordingly.

Here's what I came up with:

Kool. If I didn't get the help I probably would've attempted what I had mentioned earlier.  Yeah I definitely need to plan prior to doing anything. Thanks for your help man. It's nice to know that help is available. 

Haha, thanks! I'm in IT, I love Visio

Its quite possiable to hide that amp your talking about under the rear passenger seat. From the photos I saw of the rear panel removal there seems to be plenty of room under that seat.