Yes, you've mistaken the shit w/ shit. Thermalright makes the SK6, SK6+, SK7, AX-7, SLK-700, SLK-800, SLK-800U, and SLK-900U heatsinks. Except for AX-7, they are all Cu.
Thermaltake on the other hand makes the shitty volcano series heatsinks that a lot of people likes 'cause it comes w/ the auto rpm adjustable smart fan.
Google for SLK-900 reviews, they are popping up left and right this week. Here's one by Overclockers.com to get you started. Check out their heatsink ranking table also.