Moving the database onto dedicated hardware will definitely help but I don't think you should wait on the opcode cache, though. It really is a "turn it on and forget about it" situation. It probably took you longer to get these screen snaps than it would to get APC or eAccelerator running. There aren't any downsides and it takes almost no time at all to get it going.
As for your graph, I don't see anything that would be particularly concerning. It didn't max out the processor. It looks like it didn't even make it above 75%.