I can recommend Rocks as well, although you WILL need the slave nodes to have disks in them (you could scrounge some ancient 40Gb drives from somewhere...) you seem to want hardware information so...
First point is to have all the fans pointing the same way. Large HPC's arrange cabinets back-to-back, so you have a 'hot' corridor and a 'cold' corridor, which enables you to access both sides of the cabinet and saves some money on cooling.
My old workplace had two clusters and various servers in an air conditioned room, with all the nodes pointing the back wall. probably similar to what you have.
Don't know anything about the UPS, but I would assume having it on the floor would be OK.
Good luck with your project. Write a post in the future telling us how it goes.