Im unsure of their quality but you can have Vogtland shipped to your door for 240ish. And those are great springs. What bothers me is that the site you posted doesn't tell you that shorter rear links are required for a 1.6 drop. I'd go with Vogtland again just because they are great springs and I believe to be proven many times here on this site.
04 PI swap,SVO Supercharger 8-9 psi,Alcohol injection,39lbs Cobra injectors,XCal2-Walbro 255 LPH fuel pump,4.10 T-Lok,2003 4R70W built to withstand by RobertP,450hp JMOD,3800 circleD stall,trucool 4739 Trans Cooler,Dynotech 3.5 Driveshaft,70mm T/B,SCP Cold Air Intake,90mm LMAF,JBA headers,Magnaflow Midmount,No cats with 3inch piping,Vogtland 1.6inch drop,Cobra R's and xenon body kit.