SQ performer?

I'm bias.  But I don’t think anyone here will tell you JL Audio doesn’t make some great stuff.  I’m making some assumptions:  1. you did not mention you needed a head unit, so i assume you have a good one.  2.  I assume you will install it all yourself and just spend the 1g on strait components. 3.  I assume you wanted to go with one brand throughout the vehicle.  So, without further rambling form me here is what I would do with 1G in a sq setup:

Upfront: http://www.jlaudio.com/evolution/XR570CS.html#

Subwoofer: http://www.jlaudio.com/subwoofers/10w6v2.html

Amp:  Either this: http://www.jlaudio.com/amps/4504.html

Or these:  http://www.jlaudio.com/amps/3002.html  http://www.jlaudio.com/amps/5001.html

If you want to save a few hundred bucks, try this subwoofer substitution.

Subwoofer: http://www.jlaudio.com/subwoofers/10w3v2.html

The 10w3v2 listed above mated with a "stealth" box.

Stealth Subwoofer:  http://www.jlaudio.com/stealthbox/EXPL2.html

I (and everyone else from the looks of it) say a JL.  Go with the best one you can afford.  None of their subs are bad.  Look into their amps also.  For the component speakers look into Polk MOMO's.  They have some really nice stuff and sometimes (according to who you talk to) have a better rep w/ sound quality and power handling.  JL isn't cheap but for the speaker/parts you get from them every penny is worth it.  JBL makes some nice amps.  Also Infinity makes good speakers and subs.

And I'll recomend a sub: my little (literally little) favorite:

     http://http://www.jlaudio.com/subwoofers/8W7.html

No need to say anything just read the specs.  And not a bad price on them.  You'll probably need only one for some good bass.