Thanks for your advice.
I already have two dedicated servers in the manner you've described, both are E3-1230v2, 16GB RAM. The webserver is nginx/php-fpm and filesystem resides on 7200RPM in RAID-1. On the mySQL server, OS runs on 7200RPM in RAID1, but database is housed on 120GB SSD in RAID1.
I've been running on VB 3.x for quite some time with my community (2007, originally on 3.5) and am considering a move to either IPB or XenForo.
There were a number of difficulties with vb 3.x, mostly considering the size of the posts database (677K thread, 26M posts).
How does XenForo's...