Scheduled reports causing slowness in XIr2

Is it common that once a certain number of scheduled reports are running that the system slows down dramatically? Our config is:

2 W2K boxes in a cluster, each has 2 dual-cores

Tomcat/Java

Oracle

Beyond having limited the max jobs allowed in the job servers to 10 each (therefore max 20 concurrent running scheduled reports), what else can be done?

More to the point, what exactly is causing the slowness? We've monitored the CMSs and they seem fine, nowhere near maxing out memory or processing. However, the Unix box hosting the Oracle CMS is taking a major beating while these 10-15 scheduled reports are running. Does anyone know the cause? Is this situation improved any in r3.0 or r3.1?

How have you more experienced folks addressed this problem? We have 4k+ users and obviously need to beef up the architecture, but for now we're taking a beating on this.

Thanks,

DOn