What issues are you having exactly? I mean, it isn't a regular "computer" per se (I mean, it's a computer, but more of a dedicated application appliance)... Adding more RAM won't help or make it faster... Oddly, adding an SSD won't make it faster, except minor reduction in boot times... And MXeIII already has gigabit Ethernet.
If you want it "faster" then virtualize it... It will reboot quicker and boot faster, but it's still a system emulating an older system and even on high end virtualization hardware with WAY more resources than it needs, it still is laggy and slow to do things like searches or bulk changes.
If your issue is boot/reboot times, the best way to speed that up is disconnect the Ethernet cable(s) while it's booting so it doesn't get hammered with DHCP or TFTP requests while booting. It does help, we do it in some upgrade scenarios.