Hi,
the 2000RPM can not be called silent, even 1600rpm would be more on the performance side. The 1200rpm should be a lot better if you talk about noise. Does the supplied fan slow down when it is running in the PSU? Usually the PSU has a fan controller inside it to power-up the fan if necessary, but some really good PSU power up the fan at 3v and that might not be enough for most fans. So not sure how it is with the Zalman PSU.
I assume it will be fine with Slip Stream, yet please be careful with opening and modifying any PSU - it's warranty voids for sure.
The Slip Stream should be available world wide. Please visit our
where to buy list to find the right shop.
Cheers,
Andy