This is in fact of the things I want to use XPLC for, building small, high performance servers, mostly event-driven, using message passing (similar to what David McCusker describes here) between processes for scaling on SMP systems. XPLC comes in when I want to make things even smaller and faster by putting multiple servers in the same single-threaded event-driven process, sharing as much stuff as possible. For example, you could build a server with HTTP, SMTP, IMAP and POP3, all sharing common information, including HTTP giving you a webmail interface.
I still can't believe that we can't publish a medium-low traffic interactive website on an inexpensive single process box. All you see is dual this and cluster that, with RAM going around in gigabyte slices, and still getting a slow site in the end. Try this little experiment with your web server: open up a thousand connections, but don't do anything with them, just keep a thousand idle connections open to your web server, then access one page (one thousand completely inactive users and a single active user). Watch your server crawl to deliver a single 8K file to the lone active user. Something is wrong.
I'm taking goingware's advice and testing this high-performance single-process component-based server stuff on my 486DX4/120 with 80 megs of RAM.