I went for the Sigma APO 70-200mm F2.8 EX DG / HSM MACRO and it's awesome. Still learning it and haven't taken too many photos with it.

here's alittle sample of what the new lense does.... nice and sharp :)
3008x2000 4MB photo of the Yellow 2006 C6 Z06:
http://greatsave9.smugmug.com/photos/150212440-O.jpg

But the rest were taken with my Quantamray 70-300MM at about 135mm length, with UV contrast , and I put on a Colkin Filter for some fun to see if I could get different colors out of it. I like it, not too shabby at all
http://greatsave9.smugmug.com/photos/150121091-L-1.jpg
http://greatsave9.smugmug.com/photos/150078498-L.jpg
http://greatsave9.smugmug.com/photos/150049613-L-1.jpg
http://greatsave9.smugmug.com/photos/150081021-L.jpg
http://greatsave9.smugmug.com/photos/150135660-L-3.jpg
http://greatsave9.smugmug.com/photos/150176610-L.jpg
http://greatsave9.smugmug.com/photos/150075173-L-1.jpg
http://greatsave9.smugmug.com/photos/150074982-L-1.jpg

Love that first photo with the fisheye! I'm afraid I'm out of the loop with auto racing; what's AutoCross?

Thanks, its pretty much regular cars and regular people racing around a track at different places, either a real track, or parking lots. They usually setup with cones and you take your car out and run 3-4 times around to get a best time. Either stock sports car, or they have modified classes. Its all low cost and volunteers who run it, and its all in good fun.
www.phillyscca.com