Just for the record, even if you don't have a very active forum but with a lot of posts, it still takes cpu processes because the server still has to parse everything and get everything from the db whether or not you have an active forum or not . . . As for the RC-4, sorry but we cannot support RC-4 or less unless you are upgrading, that goes to whomever uses pre 2.0.0 and not just one specific person.
As for the server load, I could understand if you were say, using phpnuke and phpBB. phpBB itself does not take hardly anything to run, I run a test board on a P100 with 16meg of ram for crying out loud! Of course it's only localhost but I run my server in to the ground.
I purposely post posts one after the other to test load. I have Python, Perl (with DBI and DBD-mysQL), PHP, Apache, mySQL. All tweaked. Enough ranting.
Seriously though, something isn't right. You shouldn't need a dedicated server to run phpBB, that's not necessary. You do need a dedicated server for garbage such as phpnuke (you should read the security warnings put out by security experts, enough to make you cry) But not for phpBB . . .