I'm thinking of investigating the Bitscope Blade QUATTRO to host up to forty boards. Looking at the details each Blade can power the boards off a single supply, which need not be at 5V with up to 3A (4A surge) power budget. Will this support a fully connected Ethernet cluster with a 2.5 250G disk per pi and sensor inputs to one Pi per blade.
This answer assumes you already understand Raspberry Pi power limitations.
Powering many Raspberry Pi's is a challenge in that they need to be properly supported and cooled. Applying 5V directly via the expansion header pins 2&4 is often more mechanically stable and electrically reliable than using the USB power. This consideration naturally leads to the use of a separate board (i.e., blade) to which the Pi is mounted via the expansion header.
A blade provides mechanical support for multiple Raspberry Pi's attached via their expansion headers. The blade will often have its very own voltage regulator for supplying the attached Pi's. The blade power supply will usually be a DC-to-DC switching regulator or buck converter (search SE Electronics), that accepts a range of DC voltages (e.g., 7-48V) provided by a master power supply.
To determine the needed master power supply for Pi blades, you will need to measure the power requirements of a single fully loaded blade with all expected peripherals attached and running actual software. If possible, include cooling as well for accurate measurement. This measurement is easily done with an inline meter. Knowing the wattage required will help you size and purchase the required master power supply for your entire application.
Although bench power supplies can serve as a master power supply, it may be more cost effective to consider dedicated power supplies such as LED drivers, which are designed to supply power cheaply and reliably over a long time. If power outage is a concern, then a battery or UPS can provide needed protection from power failure. You can even choose solar + 12V battery, etc. In other words, your own requirements will best guide your search.
The Quattro has its own integral switching power supply to generate the 5v supply to the Pi computers. The current rating of the external supply for each quattro board will depend on the voltage you provide. At 9v it will need 4A; at 48V it will need just 500 mA.
You might want to consider using a UPS if you want to ensure a safe shutdown of all the Pis in the event of mains failure.