This would most likely be funded by a grant from SRP if we are able to win the grant. As such, I would have to have a quote in the application from a retail location for the items and I would need receipts at the end of the purchasing timeframe. Due to these requirements I cannot go through used items for this project.
As far as the all in one, it just seems simpler in terms of getting everything that is going to work well together, the stand will be well organized and managed, etc. Although I have my own 110g at home I would rather not deal with the issues of non matching sets for tank/stand/sump/skimmmer/lights/pumps/overflows/ATO.
That being said, if Red Sea or another manufacturer cannot offer us a better deal than the $4000 retail for the S 500 I may be forced to part the purchase out anyway.
Since teenagers will be putting this together under my supervision the all-in-one with explicit instructions may be better/safer as well... we'll see!