First: this is a really interesting thread and I have a lot of respect for your experience.
But is it really better to statically allocate resources to threads? You may have 8 cores on a box and 1 of them burning and 7 of them cruising. By utilizing a small thread pool and letting the scheduler spin things off dynamically you can turn that into 8 cruising instead.
Just curious.
The networking thread shouldn't be using hardly any CPU. If it is, then somethings badly wrong. It's better to have a single networking thread, trawling through the connections, moving data around, and have it talking to other threads that handle long jobs, cpu intensive tasks, or anything that might block.
But even then, it's better to have a set number of threads doing different tasks, rather than one per user. eg have a network thread, a db thread(s) etc.