I'm no expert in the graphics department, so still looking. Dell does not specify everything, and these cards can be configured in many ways, typically the memory can be supplied by three different manufacturers just being one example. For now, have a look at
this Benchmark website where many people have tested your current graphics device based on the pcids produced by the lspci command.
On this web page there are links that may be of interest, such as "Compare alternatives" and "See where your GPU ranks". Important notes to keep in mind while looking at a new card is your bus being PCIe 2.0 as there are PCIe 3.0 cards in similar category. Also look at minimum power supply required for any card you may be interested in, I was unable to figure out what size power supply your computer has from Dell's site, it may be 300 watt or 400 watt, this is important to know before purchasing a new card as you may need to either upgrade your power supply or downgrade the video card if looking at a newer model.
There are literally hundreds of cards available that you can use with your system, bus type and power supply size are important factors. You can always take the side of the computer cabinet off and should be able to see what size power supply it has, the size is usually visible without taking anything else apart.
I don't do gaming, but I do photography and a good graphics device makes a big difference for me when doing exposure corrections on my work. Knowing what you want from a graphics device also makes a difference, most often, we tend to go overboard.
Hopefully someone else will chime in their knowledge.