Suggestion for a very fast postgresql machine?

[Palle Girgensohn]

Hi!

Do you have any suggestions for building a really fast machine with the 
sole purpose of running postgresql for a multi user application? The 
database currently has a 11 GB footprint on the disk.

I'm thinking in terms of at least four CPU:s, 12 GB RAM. Hardware is mostly 
a matter of money, I guess, and disks are probably the bottleneck, right? 
We are currently a FreeBSD only shop, we have very good knowledge about 
that system, and no experience with Linux. Still, is FreeBSD 6.1 a good 
choice, or will a Linux distribution outperform for 4+ SMP? I won't have 
much time to experiment, unfortunately, but I'd love some pointers or tips.

Thanks
Palle