Scott - what is power draw are you getting from the 4 nodes setup you have in EL4000? I am debating about downsizing my current lab using the same setup.
My EL4000's onboard power meter claims around 120W average. That seems high if it's a per-node number, but low for 4 nodes. So I'm not really sure how much power it's drawing.
However, I also have an EL1000 with a single M510 sitting here. The EL1000 is the single-node cousin of the EL4000. This one has 2x 32G DIMMs, 1x 1T Sabrent Rocket 4 M.2 SSD, a 500W AC power supply, and a 2x40G ConnectX-3 card installed. Since it has a single node, it's a lot less ambiguous, and it's also plugged into a metered PDU at the moment. So I have good data on power for it.
With the M510 off, the chassis draws around 21W. Booting Ubuntu 22.04 over the network (via iLO) peaked around 110W, and then dropped to ~82W while installing the first time. It kept getting louder and louder, and I finally realized that I'd left it sitting with the fan intake blocked. Oops. After that, it dropped to ~63W while installing and 53W at the Ubuntu login prompt. So I guess it *could* draw ~20W for the chassis, ~7W for the Mellanox NIC, and ~26W for the M510. That'd make 120W for an EL4000 possible.
FWIW, the EL1000 is kind of neat, although I wish it was small enough to fit 2 onto a 2U shelf. As it is, it's the size of a moderately small desktop PC (7 liters--not tiny, but compact). 2x PCIe x8 slots, 1 PS, 2x 2.5" SATA bays, 2x optional Mini-PCI slots for WiFi + LTE. Unfortunately, all I could find for cheap was the 2x 1G model, but there's a 2x SFP+ model out there somewhere.