Shouldn't be a problem. That's an optiplex 390SFF. The small PSU is because of the limited bays and expansion slots in the small size case and a 95W CPU limit. GTX 1050, or even a 1050Ti low profile would be much better.
Officially that supports i5 CPUs. At userbenchmark.com I see some of them running i7 2600K, i5 2500k, i7 2600 CPUs.
http://www.userbenchmark.com/System/Dell-OptiPlex-390/1958