Suggestions Needed & Welcome

kickers are good for the price, get the higher end ones though, thats all i can suggest since thats what i got.
Maybe someone else can chime in

Alpine Type R's are good and you can sometimes find them on ebay or sonicelectronix.com for around $100 but if your on a tight budget I would go with one good sub with the right amp so that it is getting all of the power it can handle. I got an older style type R 300W RMS from craigslist and it hits hard but the newer ones are 600W so they should sound nice. My brother put a Pioneer Premier Sub in his friends car and it pounded but I can't vouch for the quality I haven't had a pioneer sub. This is the sub: http://www.sonicelectronix.com/item_9238_Pioneer+Premier+TS-W3001D4.html
It seemed really nice though and it is HUGE even compared to my type R.

For the highs and mids it depends on what you have now and how happy you are with it. If you think that it sounds ok then you should be fine as long as the sub doesn't overpower the speakers so that they get drowned out then you would need a 4ch amp for them and maybe new speakers.

You know what just let me know what your budget is and I can let you know what I found in that price range that should be decent. I looked into a lot of stuff when I got my sub and I helped my brother put that system together for his friend. Let me know what you already have too and what you need like headunit, speakers, amp, box, wires.

11 bucks.

This looks like a good amp:
http://www.sonicelectronix.com/item_6522_Hifonics+BXi+1206D.html#
Or:
http://www.sonicelectronix.com/item_9551_Hifonics+TXi+1008D.html#top
But I haven't had too much experience with Hifonics but they are supposed to be good quality.

And for 2 10's I would pair it with:
http://www.sonicelectronix.com/item_6474_Alpine+SWR-1042D+-TYPE+R-.html
for 2 12's:
http://www.sonicelectronix.com/item_4281_Alpine+SWR-1242D+-TYPE+R-.html
You should wire them at 1ohm since the amp is stable at 1:
http://www.the12volt.com/caraudio/woofer_configurations.asp?Q=2&I=42

If you want to go with one huge sub than that Pioneer would be good but I am not sure of the quality. I do have 1 12" type R in my car and it sounds great. Different boxes have different effects on the subs. I have only used sealed but my brother used that Pioneer sub with a bandpass box. The bandpass is supposed to make it louder and the sealed has better sound quality. Even if you haven't installed a system before it isn't too hard you just need to run wires and you can find all of the information you need online.

Do you have a BOSE system? The car that my brother put the system in was a 2001 Acura TL and the BOSE speakers sound nice once you take the bass off of them. If you don't then I would go with new speakers. For a headunit I have only had Pioneer in my cars and I love them but I know a few people with Alpine decks and they are really nice decks. If you upgrade the speakers you might want to get a 4 channel amp to power them but you can always install the subs, deck and speakers and see how it sounds then you can decide later. I don't have a 4ch amp in mine and it sounds fine but that will be the next thing I upgrade.

If you don't have a BOSE system you can get either components or regular speakers. Components are a lot nicer but regular speakers are a lot cheaper. I would stick with Infinity speakers for good quality at a decent price. You could also go with alpine which is supposed to be really good and pioneer which is good.

For the shape I don't know too much about that but a larger surface area means that the sub can move more air that is supposed to be the reason that Kickers are so loud.

Yeah just let me know. I don't have a ton of experience but I have put together a few systems and found a lot of information while I was putting them together.

MKB has some good recommendations. I acutally have the Hifonics Bxi1606D which is a step up from that 1206d running my subs and for highs I am running the Txi4008. Sonicelectronix is a very good site to order from. They package there stuff very well and arrives promptly. I bought my entire system from them. Very impressed that the sub box arrived undamaged.

subs
http://www.sonicelectronix.com/item_6336_Hifonics+BXi+1606D.html

Highs
http://www.sonicelectronix.com/item_11201_Hifonics+TXi+4008.html

I would go with two separate amps. I dislike running multi channel amps to subs. Always run a mono block amp to your subs which is a one channel amp. Unless in situations where you subs cant handle a mono block amp or you cant afford one then i guess a two channel but a 2 channel amp will push subs just fine but a mono block amp is more efficient and stays allot cooler while putting less strain on your alternator.

yeah, throw in a after market, if u need help, im in the V, and i can prolly help u install errything

I don't really think that is true since the deck will only provide the audio signal that amp will do all of the power. But you should put in an aftermarket deck so taht you get better sound quality with your speakers and it will give more power to the speakers if you are not using a 4channel amp. What kind of system did you end up deciding on?