hercules rmx setup HELP!

ok i don't get this at all. i have a hp laptop with a amd 2ghz processor and 3gb or ram. im running the rmx sound card in asio mode. my settings are 41000khz 16bit and no mater what latency i have it at the sound stutters like crazy. i then set it to 24bit 48000khz and im running the latency at 21ms and theres no problem at all. why is this, wouldn't the 24bit setting be harder for the computer to run. whats the proper way too setup a sound card. what should my latency be at or how do i chose the right latency. sorry for all the questions but a bit new to djing and im trying to learn everything at ones lol. im having a blast and thats what counts .