126.9 et al:
IMO the server performance problem is because PPRuNe is so popular - kudos to Danny for kicking off something and only asking for contributions for the frilly bits around the edges.
I've made the point before, but I've made it again. Too many people connecting to one server means the server has to keep track of lots of individual sessions at the networking level, long before any data reaches the database / vBulletin software. It's this which impacts performance - lots of people, lots of connections, lots of processor time keeping track of them and lots of memory too - all leaving less time for the main work.
Upping the processor will help - and as others have said, if you're not paying for the service, you can't really bitch about the poor performance.