If u are going for Lumia 530 then u need not to go. U will downgrade. Rather u should wait for more time to get better handset. Else u can upgrade now to lumia 630, 638,535.
520 is anytime better. Has 720p video recording, unlike 480p of 530, so i don't think the processor is upgraded. I think dual core S4 is better than quad core 200. Also 305 is better than 302 as GPU. And 520's design is better. I bought a new 520 for dad just few days ago.
Between 520 & 530, I consider the 520 to be a clear winner as the only real upgrade is the quad core vs dual core & it still performs swell. So stick with the 520 & wait for 535.