The plain fact if you have a bigger than OEM supplied PSU wattage wise, it always helps. Of course, it works better is a qulity type PSU. Alas, it must also be physically be able to fit, etc. to install. I mention that as some unique PSUs are out there and that's a consideration before the purchase. Also, if a larger wattage PSU is installed, it will provide for wider range of GPUs to be gotten from. I wouldn't go crazy putting a super-hot GPU whose demands require yet more cooling ot simply added attention to keep it going. Also, if Dell states that works, that's a "go" to proceed. usually they're conservative in order keep any problems out of the loop. Anything else is on you, so think this all out. Also, being a mini or small factor size PC, they tend to be restrictive to upgrade unless as stated above. You should have not brought this if you were going to up-size the PC from the git.

tada -Willy Happy