I have no experience with that kit. But, I do believe it will be a huge improvement over stock. I went with Steeda Sport Springs and Koni shock/struts and the improvement was massive. The Brembo suspension really isn't very good, only slightly better than non-Brembo. Actually, they both suck and a suspension upgrade is needed either way IMO. Whatever you do, don't go the "rear springs only" route.
2011 GT Premium / Ingot Silver / Comfort Pkg / Brembo Pkg / 3.73 / SW off-road X pipe / GT500 Axle Back / Steeda Sport Springs / Koni STR.T struts and shocks / UMI adjustable panhard rod / DG Custom Louvers / Graphics Express Hood and Trunk Stripes / Steeda CAI / BAMA Tunes 89, 93, 93 (ghost cam)