Here is another option to run the CTSV calipers on the solstice. ZZP make this kit for the cobalt, and as we know, the cobalt brembos bolt up perfectly fine to the solstice. Do a direct replacement for them, is a direct replacement for us. Only issue is that you need to already have wheels that will clear a thicker caliper. Another unknown is the rotor center bore...if its 65mm then it needs to be honed out to 70mm.
ZZPerformance - 14.5 inch Front Brake Kit #ZZ-145CBK
And another option im researching now, but am about 90% sure will work is using the ATS 330mm brakes. The mounting hats on the calipers are exactly the same as the solstice and the rotors already have a center bore of 70mm. The only thing we would need to do is again, have wheels to clear them, and re drill the 5x110 pattern.
for the rears im looking into using Volvo S60r rear calipers. This would mean losing the parking brake...but I have a auto, don't think i use that thing anyway