[horde] Bottleneck ? CPU or HDisk IO or RAM

[Linux Advocate]

Guys, just wondering. For a horde groupware webmail edition, what will be the bottleneck if there are about 1000 users? The CPU ? or the HDisks?

Will a new box with Dual Core Dual Xeons,  8GB RAM and 7.2k rpm  750 GB SATA disks ( 6 )  be sufficient?
Anybody here got some sample specs of some running machines with the groupware?

Thanx in advance.
Marco.