For Sun boxes you don't really want a KVM, a Terminal Server (also called Console Server) is a much better solution. That way you can access your system's console from any computer on your network, not having to be physically there in the datacenter. They are more expensive, but for managing gear with a serial console they are much, much better. Also, Sun servers generally don't have a video output, so you'd have to buy and install video cards before you could use a normal KVM switch.
Here are a couple links to get you started.
This is for an 8-port console server. I used one of this brand at a previous job and they were decent.
http://www.42u.com/consoleserver-800.htm
And here is a 8-port server from Avocent, which is a leading brand for this kind of stuff.
http://www.avocent.com/web/en.nsf/Content/CPS810