You've mentioned two webservers - Apache and IIS. The Ruby folk don't use either - they use mongrel+lighttpd and seem to do just fine. There's at least 3 other webservers that probably have some decent work behind them.

There's also yaws, written in Erlang. Early benchmarking seems to indicate that yaws can handle something on the order of 40,000 simultaneous connections per machine compared to Apache's 8000. Having been written in Erlang, it is pretty simple to have it take advantage of multiple machines.

Furthermore, it sounds like you're starting to go beyond the simple stuff that most webdevs can do and get into the kind of stuff an expert is really needed for. Kinda like how most devs can configure a basic RDBMS (like MySQL, PG, or Oracle), but really need a DBA in order to take full advantage of the relational calculus, how it's implemented in the chosen server, and how to properly configure it for real-world use. This isn't a slam - different people specialize for different things. I wouldn't hire any of @Larry to configure a RDBMS, but that doesn't take away from any of their real skills. Same thing goes for any portion of your service's delivery stack.