I've been working out my wall unit on paper and come across the idea to use 8 ft Fluorescents over the top two 4 ft Vivariums and over the lower two 4 ft GH style terrariums. Certain 8fts have a fantastic lumen output if you check out the specs here:
My Home Depot carries the Alto 841 tube (6600 lumens/75 watts) and a couple of the other nice high lumen/full spectrum tubes listed above. The 8 ft fixture is $37.99 and two nice output tubes are $18.99 per pair.
This brings my whole lighting setup for the four vivariums to apx $160 for four fixtures (two twin tube fixtures per shelf) and apx $80 for bulbs if I don't order them online, which looks like a better deal - but I dunno what shipping would be on a box of 8 footers. Total 8 Ft setup is apx $250 with taxes across the street at HD. Compared with apx $800 for four 6 tube T5 fixtures, bulbs and shipping.
Using this configuration gives me apx 24,000 lumens per shelf (comparable to a 400W metal halide lumen output) but using only 300 watts per 8 feet compared with apx 30,000 lumens/340 W of T5 for only 4 feet. Not only will startup be 1/4 the cost but my power bill will be drastically reduced and I will not be loosing much in lieu of lumens. And to slap another fixture over each shelf wouldn't cost much should I actually need to go up to 36,000 lumens per shelf.
Anyway, it's all still in planning but I thought this was pretty cool to find that the big industrial FL bulbs have a pretty darn good output if you have the space to use them.