Well, if space is of no concern, get a better case and motherboard for less:

Case
Motherboard

The benefits:
Bigger case equals better air circulation, runs cooler
Note that the case has a big fan on the back
The case does include a 500W PSU, double of the mini case
The mini case motherboard has on-board video (which you probably will never use), with can mean that other MB components are of a lesser quality

With the extra money I strongly suggest you get an 8800 GT video card, specially if you are going to 5-box:

Video Card

This will run you about $50 over, but I think it is worth it.

If you have another $60 I would suggest memory that matches the MB and the CPU 1066MHZ FSB:

memory

This will kick the speed up a notch

Edit: you will need a 64 bit OS to use the full 4 Gigs of RAM