I managed to get Asterisk up with FreePBX. Compiled from source - the rpms don't play nice with the current version of FreePBX. It takes a damn long time to build from source on an Atom machine... Next job is to hook up the SPA3102 as an analogue extension and a pstn trunk.

Bought a pair of HP 2650 switches on eBay - very cheap. Unfortunately they weren't packed very well, so the front bezel and GBIC slot on one of the switches are smashed. The seller was very good though. They partially refunded. These are layer 3 capable and should do well sitting behind my ESXi hosts.