I managed to pick up this switch for around $1200. I think if I waited / made offers on more I could have found one for a bit cheaper, but it seems like a good price.
I'm happy with it so far, but still in the process of setting it up. With fan speed set to 30% it's quieter than the ex4300-48p it'll ~displace (*), and temps seem to be staying safe. It's also happily running with two kingston 8GB ddr3 ECC udimms, bumping the memory from 8GB to 16GB. It has an m.2 slot that I'm not putting to any use yet, but I'll throw one in before I rack it just in case I get curious what it can do.
It'll be my new homelab(/home) core switch - so far I've been trial-and-error'ing my way to find the right permutations of QSFP->SFP+ adapters and xvcrs that it'll allow me to coerce to different speeds to interconnect with 1G devices (a netgear poe switch + my srx300), 10G switches (an ex2300c), a 40G switch (ex4300), and various devices in the rack via DACs and breakout cables. So far it looks like the key is to just get a transceiver that's the right speed to start with - e.g. it doesn't appear to let you force a 10G transceiver to negotiate 1G.
And no, the irony of using 1G optics in a 100G switchport is not lost on me, but with breakout cables and 32 ports to go around this should work nicely with only about 50% of the ports in use for now.
@liampatterson I'm assuming you've found this by now, but I found a kit including the inner rails
on ebay - seems there are more than a handful available.
(*) The ex4300-48p was a fine switch, but the poe version is too loud for my environment. It gave me a taste for 40G on a few machines, but ultimately didn't provide enough in the way of 10G interfaces. Now that I've moved all my POE devices to a less fancy netgear poe switch, I'm swapping in a non-poe ex4300-48t for 1G connectivity, which will cut down on noise/heat/power demand. The 7060cx is also replacing another (unexpectedly hot & loud) netgear 10G switch that I had put in to augment the 4300's 4x SFP+ ports and inability to use breakout cables.