upgrade from version 9.4.7 to 10.2.4 CPU question

We have several 6400 F5 Big-IP appliances on version 9.4.7 and are trying to decide whether to upgrade to version 10.2.4 or to buy new 10200 appliances. Once concern with the upgrade is CPU utilization. On our busiest appliance, sometimes the CPU periodically spikes to 100%. The average CPU utilization in the GUI performance graph is between 60-70%. We also use Solarwinds to monitor SNMP and the average there shows 88%. We are concerned that an upgrade to 10.2.4 may cause an increased load in CPU and cause performance issues. Does anyone have any thoughts or experience with a similar situation?

Thanks.