How many Baht in a Tuk-Tuk from Hualampong Train Station to Khao San Road in Bangkok?

How much should my girlfriend and I pay in baht from the Central Station in Bangkok to Khao San Road in a tuk-tuk (each with backpack)?? I've done it before (I know it will be a little crowded with the backpacks though more atmospheric than a taxi) but not in a 3-4 years. I'm a good bargainer but I need to know the lowest price they'll take. The tuk-tuk drivers by the station are usually the toughest to negotiate so thanks for your help!