The i3 5xx processors are rather underrated. When SB came out, and everyone freaked out over them, I picked up 3 i3 550s on various Fry's sales (average price per cpu - ~$60) and couldn't be happier with them. Two of them are in HTPCs while the other is in a 24/7 torrent and DVR box.
Each of my i3s overclocks into the mid 4s without any work. I run the HTPCs at 4 because of the smaller cases and somewhat mediocre heatsinks that means, while the torrent machine runs stock. The overclocking makes a big difference - and it should give you a very nice boost. Without sweating the overclock, you should be able to run your 530 at a rate that will put it on even footing with an SB i3 2100.