The sinister CTS-V above is the work of Katech, the firm behind Caddy's SCCA World Challenge race cars. For the SCCA events, the CTS-V is forced to keep its stock internals, but for the private-sale K-Series, Katech chucks the LS6 and drops in a custom 6.7 liter V8 good for 525-hp and 535 lb./ft. of brain-concussing torque. If for instance you absolutely had to get to 60 miles per hour as quickly as possible, the K-Series will get you there in 4.6 seconds. On top of the power boost, available from Katech as a stand-alone upgrade, the K-Series sits on an aggressive handling package comprised of bits from H&R, QA1, and their very own gorgeous one-piece wheels. Going all the way with the K-Series entails spending $38,000 on top of your CTS-V's $50K MSRP, but AutoWeek makes the argument that it'll still be less than the new BMW M5. I will make the point that Katech's creation is (ahem, arguably) better-looking, as well.