Can I go any lower? Rear suspension geometry
 

http://i.imgur.com/bJrzaAb.jpg

This is what my rear control arm looks like. Am I already compromising geometry. Would like to get another 1/4 inch or so if possible. All stock in back with coilovers.

You would be fine at the height your looking for, just recommend adjustable lower control arms or camber bolts in the long term if you want OEM geometry and camber adjustment, other than that your good to go

Get LCAs from Stance or PBM where they lower the coiler mounting point by 1-2". That will allow you to raise the height of the coilover, but keep your current ride height.

After that, your options are to either raise the subframe, or add rear drop knuckles.

This will give you bump travel, but does not improve suspension geometry.

To the OP, I wouldn't go any lower if handling is a priority.

- Andrew