how to pick subs, mids and highs?

Before you delete my post, if I did this wrong please let me know, I did not see a "How to pick sub's" topic unless I am just blind

I want to upgrade my 2 Directed/Xtreme 12's for some 15's, what would you all suggest on a budget of 150 each, they will be run by a TMA 1000.1

or

Question #1   

would I get more by adding another 12 and running at 1 ohm since the amp is stable at 1 ohm and pushes 1000watt

Question #2

What brand of "inexpensive" would be best

Fosgate #3

MA (is this like BOSS or is it a decent brand)

Directed/Xtreme

MTX (a little steep for me)

Pyle DRIVER (these were good back in the day, but what about now?)

Question #3

When you buy for instance,

15" dual 4ohm voice coil

will that give you a 2 ohm load or a 4? I know that running 2 each 4ohm subs gives you a 2ohm load, but how does it work with 1 sub with dual voicecoils?

I do not really know what to get, I am not wealthy but don't want audiovox or BOSS or crap, I wish I could get some Cerwin Vega's, but I have 3 kids to support ....lol

so far, going from "looks" and written specifications and price, I like the

PYLE blue series 18" PL1890BL,

MA audio MA183XE

but that is simply by specs, price and looks, please advise

I found some nice Blaupunkt 3 1/2 on the Sonix site but they are only rated at 35RMS

right now I have the mids/highs running off the deck which says it is 80w x 4, what do you think it is really putting out? it is a PYLE PLD51MUBT, I cannot find anywhere something that specifies the nominal output ,,,but I am upgrading to  TMA 320.4

Correct.  MA Audio is a Taiwanese company that used to be called "Mobile Authority."  Not very reliable.

$300 for a pair of decent 15's is relatively easy to find.  I assume you plan to build a proper enclosure for them?  Take a look at Memphis PR15's, JBL GTO's, or a pair of Kicker CompVRs.  All of those you should be able to find for less than $300 a pair.  I recommend DVC 4-ohm drivers so you can wire for a net 4-ohm load on your amplifier.

what about these, for mid's, I have some 12's by them and they are pretty decent

http://www.sonicelectrnix.com/item_14036_Xtreme+Audio+500X.html