Don't insult us with Xserves and say that the two are comparable. Does the new Mac Mini support ethernet bonding? oh wait, it only has one ethernet port.
Here is the solution: place second Mac Mini on top of your current Mac Mini. If you are trying to run more than 100 shared sites off of one Mac Mini than you really need more than one Mac Mini.
You said it yourself, the keyword there is "two". 1 X-Serve < 2 Mac Minis.