A GT 1030 would allow you to connect a 4k monitor/TV to that ancient system. Because it has PureVideo "Feature set H" it can fully hardware accelerate 4k videos in H.264 AVC, H.265 HEVC as used in Blu-Ray, and VP9 as used on Youtube. There's simply no way to smoothly play the latter two on such a system without such a card.
Note this card can decode the above formats for viewing, but cannot encode them in hardware so this is not a card for video content creators, who would presumably be using a faster system anyway. I would not suggest a CPU upgrade as the fastest is only 3.0GHz and would not allow the system to do anything it cannot already do.
While you probably don't play any games on it, the GDDR5 version of this card is faster than anything you could have bought back then, even ~300 watt cards requiring two power connectors, while only using 30 watts. So it is perfectly suitable for vintage games too.