I just had mine lowered last week. Suspension Max also has the identical SpringTech kit currently listed on eBay for $329.95 + $53.95 shipping.
http://cgi.ebay.com/ebaymotors/ws/eB...K%3AMEWAX%3AIT
I did not change the shocks and Suspension Max did not suggest or recommend that I do so. The kit comes with lowering brackets to relocate the stock rear shocks to accommodate the shorter springs. They also said the rear air ride suspension and shocks would continue to work as normal after the kit was installed and they do not anticipate I will have any problems. They also said I will have no problems returning the vehicle back to stock if I have someone reinstall the stock spindles and springs. So far everything appears to be working as normal and the air ride compressor runs and levels the car when it is started. They just told me to drive it for about 50 -100 miles and then have it aligned after it settles. You will not have rubbing if you stick with the stock tires. I have 24s with 305/35 tires so the wider tires cause the rubbing
Before settling on the SpringTech kit I also looked at the following:
McGaughy's
http://www.mcgaughys.com/tahoe.html
DJM
http://www.djmsuspension.com/
Ground Force
http://www.groundforce.com/default2.html
Eibach
http://eibach.com/cgi-bin/htmlos.exe...27051600019949
Belltech
http://www.belltech-sport-trucks.com/
I would suggest you check them all out and decide which one is best for you. In the end I went with the SpringTech kit from Suspension Max because I could get it cheaper than the comparable kits, they are the actual distributor for SpringTech, they are in my local area plus they offered professional installation, warranty and support.
I will warn you it takes some getting used to it after it's been lowered especially after you're used to seeing it and driving it at the stock height. The first time I saw it lowered it looked really weird and then I got behind the wheel and it seemed like I was sitting so much lower than before. At first I did not like it and almost decided to have it put back to stock. But after a few days I got used to it and now I think it looks so much better without all that space between the fender and tires. For my taste though, I would not go any lower. Suspension Max also said the rear spring will sag another 1/2" over the next few months to level the vehicle even more.