If so, what could you recommend?
for ETH - RX cards 470/480, 570/580 some are using 550 and 560, Gtx Cards 1060,1070, and ti's some are using 1050
The real deal is how to get them with reasonable price and when will the stock be available
Can I keep my motherboard?
actually not sure about it, old mobos some might work some may not particularly on the x1 pcie slots, although mining doesn't require high specs Pcie