You could run it passive yes but better to cable tie a 120mm fan to it.It comes with 8x memory ramsinks you stick to the memory chips.It has voltage regulation chips which ideally should be covered too (a grey area really I am not sure if anyone is 100% sure they are needed) in which case you'd need to buy that zalman ramsink kit.
http://www.overclockers.co.uk/showp...me=Zalman ZM-RHS1 Silent VGA RAM Heatsink Kit
I am using an 800rpm 120mm fan on mine and get 35-40c idle 45-55 full load dependent on room temps.
It's very easy to change, easier than installing a cpu probably, just unscrew the screws on the stock heatsink click it off then clean everything up then stick the ramsinks on, then put the heatsink in place and tighten the screws much like a cpu cooler.
So if you have a spare 120mm or even 80/92mm fan floating about use that and cable tie it to s1 heatsink 2 corners of the fan will do.
In this pic you can see 4 grey chips 1 ramsink can cover the top two and 1 on the bottom 2 and the little black chips 1 ramsink over top 4 and same with bottom 4 so really all you need is an additional 4 ramsinks.
The memory sinks are the black chips on the left hand side around the processor.
some people say the memory sinks which come with the s1 have bad thermal adhesive but they will stick on fine if you clean the memory chips up with some good tim cleaner.
This bit on the right hand side are the voltage chips, what someone has done here is hacksaw off the stock cooler and kept the right hand side
You could do that with a hacksaw or alternatively get extra ramsinks like I did and use 2 per 4 voltage chips
