Like was said, the ethernet is not 100 Mbps on RPi. It's closer to 20 Mbps. If you start buying accessories, consider cubietruck. It comes with wifi and so on. Rasberry soon becomes really expensive once you start stacking gear and also the 2 usb ports are soon full. You need a powered hub if you ever consider more than 2 USB devices. Those are not that cheap.
Please also consider the userspace is a sh*t to work with since the CPU is so slow. It won't get much better if you emulate with QEMU. And you need to do development somehow in that ARM6 environment, cross compiling just won't work with all problems.