I went with Steeda and have nothing but positive things to say (handling AND ride quality).
The car feels very solid and planted at all times. Aggressive highway speeds and maneuvering are much more safer. Imperfections in the road can definitely be felt much easier, but the stiffer ride 'absorbs' them well so ride quality actually improved instead of worsening. I haven't gotten to sway bars yet, but I can already take much more aggressive turns and my friends have even noticed it as well.
I DD with all the suspension mods in my sig and I'd say its easier to DD my GT with the new suspension vs. the stock suspension, but that's just me.
2010 GT Premium - Automatic - Torch Red