Hardware for replace my UTM

Hi all, I need any tip for purchase 2 new server for replace my UTM Sophos v9.

The hardware current is 2 HP Proliant DL320 G5, 1 x Dual Core 2.4 GHz, 8GB RAM, 2 HD SATA 250GB on RAID 1.

The services active are:

Firewall, IPS, Anti-Portscan, Web Filtering, SMTP Proxy, Wireless Protection, 3 Site-to-Site VPN (but the traffic is really limited), 8 x Remote Access, Web Appliance Firewall (for CRM, Web site and in the next days OWA), HA/Cluster, Antivirus for HTTP/S, SMTP, WAF, Antispam and Antispyware. There are 7 VLANs and 4 wireless network with 1 x AP15 and 1 x AP10.

There are 50 users.

Sometimes, lately more frequently, the CPU usage go to 100%, which makes it almost impossible to navigate, so I have to disable the IPS and restart the HTTP Proxy to get it back to normaly values.

The candidates to replace them are:

 2 x HPE ProLiant DL360 Gen9 servers with the following specs:

- 1 x Xeon E5-2620V4 2.1 GHz

- 16 GB RAM

- Intel Corporation 82571EB Gigabit Ethernet Controller Quad port (current installed on my UTM)

- SSD to be defined (some tip??)

This configuration is oversized? What should I change, maybe to reduce costs?

Thank you for any help!