Hotchkis is probably fine although Moog springs will be the best price anywhere. Check other threads for the word Moog. Most of the aftermarket springs don't tell you what you are buying they just want you to trust them. They mostly increase stiffness over stock by about 20%. A moog 5658 will increase it by 25% and lower the front by maybe an inch. It depends on how soggy your stock ones are. The 5660 is 50% stiffer, I just took some out of my car and swapped in the 5658s. There are at least 3 Moog cargo coils (variable rate) rear springs to match these front springs.
Are you out for a certain look or do you want the car to handle well? Changing the front springs is not for the faint of heart, I hate doing that job personally. The rear springs take 30 minutes tops. Take the time to replace all the original rubber bushings in the control arms, it makes an enormous difference. You need good shocks (no Delcos, or muffler store brands) or you are giving a lot of handling away.
It took me 5 hours to change the front springs alone. The previous time it took me about 12 hours per side on the front to pull the spring, replace the bushings and balljoints and replace everything.
On the rear lower arms I put in the stiffer bushings that come from the the 1LE handling package on the Camaro. I use Bilstein shocks all around as well.
