Should I Buy this GPU for my PC?

[Paul_Tikkanen]

The SAPPHIRE NITRO+ Radeon RX 580 4GB GDDR5 is a much more powerful card.

So much so, that it would not work in your PC for two reasons:  It requires a 450W power supply and your PC's P/S is only 240W and it also needs an additional 1 x 8 Pin auxiliary power connector which your PC's power supply does not have.

Regarding the AMD Radeon RX550X GDDR5 in your other screenshot, the mounting bracket is wrong.  You need a card like that, but it needs the low-profile silver mounting bracket used in SFF PC's.

I don't see any of those for sale on eBay.UK but here is a listing on the eBay US site which shows an RX550 LP card with the correct low profile mounting bracket you need.

AMD Radeon RX 550 4GB GDDR5 PCIe DP 2 x Mini DP Low Profile Graphics Card R9J9P | eBay

I couldn't tell you if it would perform better, worse or the same as the GT1030.

You can do this research on your own...Google is your friend.

UserBenchmark: AMD RX 550 vs Nvidia GT 1030

Nvidia Geforce GT 1030 vs AMD Radeon RX 550 Full Comparison (techcenturion.com)

[kuplxx]

I have a problem. The RX 550 uses a HDMI port and my monitor uses VGA. How will I connect my monitor to the RX 550?

[Paul_Tikkanen]

Does your monitor also have a DVI port?

If so, you can use a HDMI to DVI cable.

If the monitor only as a VGA port, then I recommend you just leave things as they are.

I haven't found anyone yet who has used a VGA to HDMI cable and have it worked.

That is because VGA is analog video and DVI/HDMI are digital video.

[kuplxx]

Yes my monitor has a DVI port. What shall I do? Do i need to buy a DVI to HDMI adaptor?

[Paul_Tikkanen]

Good, then you are in luck.

You can buy a video cable like this:  This is a 6-foot length.

Benfei HDMI to DVI Cable 1.8m Bi Directional DVI-D 24+1 Male to HDMI Male High Speed Adapter Cable S...

Your video quality should be a little better too, now having digital video instead of the old-fashioned analog video.