Hello [NAME] ,  if your system already has 260w platinum grade PSU, then the 53w Speedster RX6400 will work fine without upgrading the power supply.  The PCIe slot provides 55w of power and Dell also tested and approved AMD Radeon Pro WX3200, which would required 65w. I think it's too late for you to edit your post but you can request Moderator to remove your service tag info from your post.
I just ordered a graphics card for my 3440 and only now realized that it requires 400 W (350 W recommended). The PSU delivers 260 W. What are my options for upgrading the power supply? It it possible? Which ones work with my computer? Are Dell parts recommended or will any brand work? The GPU is a XFX Speedster SWFT105 Radeon RX 6400. [URL]    
Power supply upgrade for Precision 3440