Personally I will only buy pants 20K or higher, although 15K+ is probably sufficient. I definitely wouldn't go any lower than that unless you plan to buy new pants every season, use waterproofing wash/spray regularly, and don't do much hiking/sitting/falling.
14 NeverSummer Proto HD . 13 Never Summer Cobra . 12 Gnu Rider's Choice C2PTX
13 Now IPO . 12 K2 Formula . 11 K2 Formula
13 NB x 686 580