single slot

I am limited by a tiny power supply (220W) and space (only single-slot cards, so no GTX 750) in an Acer AIO but want to upgrade to a dedicated GPU. I have boiled it down to: GTX 745 4gb DDR3 Quadro K620 2gb DDR3 - a higher clocked version of the GTX 745 R7 450 4gb GDDR5 - a higher clocked R7...