I went ahead and bought the unit from Ebay, 6012, with 2 PSUs.
Now I have my MCX354A cards, some passive copper cables (2m distance is fine for my home lab) and am ready to start learning. Thanks for your recommendations.
I'll be limited to Infiniband (no Ethernet without the license) but that should be OK to start with as I'm interested in SRP and IPoIB for now and I dont think those need the Ethernet license.