good integ amp match for Spendor S3/5r?

Hi,

I may be purchasing the Spendor S3/5 r monitor and would
appreciate advice on a integ amp that matches well with
these speakers. I have a budget of around $500.00 used.

I know these spendors are not the most efficient, so I am
assuming I need lots of power, like 80-100watts?

How does NAD, Arcam, Music Hall or Cambridge Audio work
with Spendor?

Thanks!