Well let's just say there is more to a "system" then just a sub and an amp for the sub. You really should spend that 1200 dollars on front stage, headunit, amps, sound deadening, sub etc etc.
Trust me, with 1200 bucks you could have a very nice comp set or active setup and still have money for a very nice sub/amp combo.
Headunit: used 8053(300 bucks)
components: Re comps are like what 160 something?
an amp for them probably 100 - 150 bucks if you shop around
sub:RE SE - 185
sub amp: orion 1200D 285 from hccafan.
now I'm just using these as an example, and don't quote me on the prices I'm just trying to give a rough example here. Shop around though, classifieds even and I'm sure you can get a killer system for 1200 bucks.