According to the hierarchy chart, and taking into account cut-down variants of some of the budget cards, in order of performance from lowest to highest:
GT 1030 SDDR4 - avoid this
GT 1030 GDDR5
Once you start getting into RX 550-640 and both RX 560 cards, though, you find that they equal or exceed the price of an RX 570. Currently in the US, the Sapphire Pulse RX 570 4GB can be had for $119.99. That's the best bang-for-buck you can get with a new card, and, even if it's more than your A4 can keep up with, you can carry that card over to a new system when you upgrade to a new platform.
The RX 550-512 and the two GT 1030 cards are cheaper, but their price/performance ratio falls far short given the discounts on some of the RX 570 cards.