Are you sure that over 5 is a problem?
I was under the impression that load average is the sum of the load on all the cores. For example, my server (bruno) has four Xeon E5405, each of which has four cores. Therefore, as long as the load is under 16, the processors are not 100% utilized. Is this correct?
(Check the processors with something like grep "model name" /proc/cpuinfo)