I'm using a long-in-the-tooth Atom D525-based SuperMicro board for a low-power FreeNAS build and I'm finally ready to upgrade. Since last year I've been eyeing the Atom C3000 Denverton chips as a huge upgrade, but I have some questions.

- I have been looking at the C3558-based SuperMicro A2SDi-4C-HLN4F board, but it's not really stocked by the major retailers any more. Why is this? Is there something better that's out now which I should be looking at?
- Searching around I've found listing for A2SDi-4C-HLN4F-O and A2SDi-4C-HLN4F-B models, but I haven't found any information about the differences on the SuperMicro homepage. Does anyone know what they are? (Assuming the images on the product listings are correct, it seems like the O has only 2xRAM slots and 1xSATA SoC plug, while the B has 4xRAM slots and 2xSATA SoC plugs)
- Will ProxMox be able to pass-through the HBA on this board without issue?