Which board? If it's the -VM then it's got integrated lan, sound & video but NO OVERCLOCKING options.
Mine with a 1800+ does WU's in 3:15 for High AR units & 4:00 for VLAR units running Win XP.
A .417 AR unit gets done in 3:47
Like I said, with no overclocking at all. So you should easily be able to do 7 WU's per day per each system. X 6 boxes should give you about 40 - 45 units a day.
If it's not the one with integrated video then you will be able to OC and get better times.