Thank you to all for the useful information; especially to Roman, Julien and Scott.
I want to make optimal use of my existing dedi rather than hiring a more powerful one, so I've set NumCPUs to 2, renice to 10 and will reboot (as the latter is an init script I guess reboot is necessary.) I will then wait a couple of weeks to see what the maximum average bandwidth usage is at 200% CPU (for two cores) and will set the bandwidth limit to just below that.
Hopefully this will improve both my Tor relay's performance and allow me to continue to use the dedi for other purposes.
Thank you all once again.
kingqueen
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