Radeon HD 7000 series - Wikipedia
en.wikipedia.org
If you correlate the "Southern Islands" features between ^ those two the 7550 card is 1080p max so it's not going to improve on the existing card that you have. I would also avoid the nVidia card (unless it's $free) because there is zero support for nvidia cards in the Generic/GBM image (our long-term technical direction) and whilst Generic-Legacy still exists and still supports them under X11 and it will do 4K, most 4K content is now HDR and X11 means no HDR support.