I have never used anything from knu but I will say this... Since I started using stinger wire I will not use anything else. Esp their power wire its true gauge, very flexible, and can be had at a good price.
DAM!!!, I need to increase my prices here at the shop. We charge $0.35 per ft here.
12ga speaker wire is $0.75 per ft here at the shop though, but when you account for shipping, I guess it evens out.
oh...I would go w/ the Knu cable out of those choices, if you need 100ft. If not, stick w/ the cheaper option. But w/ 100ft, you will have plenty left over for future installs.
I know you are probably going for a certain gauge, but parts express has 25ft rolls of Belkin 18 gauge wire on clearance sale. http://www.parts-express.com/pe/showdetl.cfm?Partnumber=109-040