How good is this upgrade?
 

My current PC specs: AMD A4-4000 APU with integrated AMD Radeon 7480D Graphics, Gigabyte GA-F2A55M-DS2-REV. 1.2 motherboard (AM2 socket), 4 GB DDR3 1333MHz CAS latency 9 1.5 V, 450W PSU.
I am low on budget and wanted to upgrade RAM and GPU, these seem to fit with the availability and my budget:
https://www.newegg.com/global/in/Pro...-314-_-Product

https://www.newegg.com/global/in/Pro...-738-_-Product

How good would be the improvement? I plan to upgrade my CPU later, but for the time being can this setup play today's era games at least at the lowest setting at 1024x768 resolution? Also, my board is Micro-ATX form, while the card is ATX form, so will it fit properly. Lastly, can I use DVI to d-sub convertor on the graphics card, because the motherbaords's site says that DVI-D to Dsub adapter wont work on the motherboard ports?

Those are fairly good upgrades. I would try and squeeze 16GB of ram out of there, but otherwise that's a solid PC and should run most games.