I like the asus b250 mining expert. The pcie inputs are grouped into 6's, with a separate input from the psu to each group of 6. I'm using a single seasonic 1300w platinum psu right now but I've only got 4 cards on that rig so far. 2 more and then I'll start a new group with another psu. 3 groups of 6, 3 psus before I need another rig build. You can see that rig here, top shelf is slotted for cards as well. Also the pcie slots are not all jammed together, so your risers won't touch each other and short it.

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