Yes, I use a MacPro 8 core 3GHZ as the Master. The Minis are connected via Vienna Ensemble Pro, which is absolutely totally awesome! So, the only hardware you'd need is an Ethernet switch. I installed 7200RPM HDs in the mInis and run all samples from the internal HD.
Examples of what I run on them: One currently runs LASS - bank presets of 10 main articulations, all sections; Kontakt set to 30kb DFD preload, which amounts to 4.3GB RAM + about 2GB for the Kontakt banks. At a buffer of 256 the CPU will max out when I use all divisi sections simultaneously in a busy section, but it works fine if I use higher buffers.
The other Mini currently holds Chamber Strings + Appassionata Strings + Vienna Saxophones - I use custom presets, but they are approximately as big as the Level 2 presets. Also uses about 6GB of RAM; similar situation with the CPUs.
VSL Chamber strings + LASS sections is a wonderful combination btw.