Absolutely.  Just make sure you get an LP version or make sure it comes with a short bracket. [IMAGE] An RX 550 saying it requires 400w PSU is somewhat hyped.  So is the GT 1030 saying it requires 300w PSU.  May be to avoid lawsuits.  As long as it's Dell, Dell 240w-290w PSU's will power up to 75w cards. In this case, I like the very low % for bottleneck.  I think the GT 1030 is a very good bet.  If you can save a few watts and get good performance, why not? In case you wondered by now: [IMAGE]  
RX 550 TDP: 50 watts intel i3-2120 tdp: 65 watts My power supply: 250 watts
Can you use a RX 550 on a Dell optiplex 990DT