The costco socks are definitely a "best buy". I love them.
I give my feet a blast of antiperspirant to deal with the sweaty foot. Liners help, but I've yet to find a sock that will keep my feet completely dry.
At $11.99 for a 4 pack, it's a sore dick.
I'll check out the Darn Toughs. Lifetime warranty on a sock? Sounds interesting!