I have no idea how large other Easysocial websites are, but ours has approx 20 000 active users (we regularly prune dormant accounts) with around 1 400 unique logins per day. We also have EasyBlog, EasyDiscuss, Cometchat, PayPlans and a few other bits and bobs installed.
We host our own dedicated server (8-way Xeon with 16Gb RAM) and with this load, we seldom peak above 10% CPU and ave RAM usage is 50%.