An I7 would give you additional hyperthreading cores. The i3-530 is a dual core CPU, stepping up to an i5 quad core would definitly give you a boost at the same or even slightly lower GHz clock. Going to an I7 is going to give you 8 total cores, 4 real and 4 virtual, which ends up being a realistic performance gain over the I5's of about 35-40% during games that support multiple cores, which is most of them nowadays, even if the game doesn't, the operating system does, so you will see a performance boost regardless. Given the prices of the I7's these days, it would be a worthwhile upgrade, the problem being they are becoming rare. Remember you need a socket 1156 processor for that board, none of the 1155 processors will work. If you can find one. The I7-2600k Quad core with hyperthreading is going for about $360 from serversupply.com, which I have ordered multiple server parts from recently. That seems to be about the best price i'm seeing on a vendor i'm familiar with. http://www.serversupply.com/products/part_search/pid_lookup.asp?pid=140332
you might be able to find a good price locally though too. Tigredirect has the 2.93 GHz i7 for $400 http://www.tigerdirect.com/applications/SearchTools/search.asp?keywords=i7+1156
You might also want to grab additional ram at the moment. a single corsair 4GB DDR3 stick is presently running $22. I can't remember what you had in there, but most games, especially things like civilization V, can use all the ram you can throw at them. your motherboard will support all the ram you can put in it, if I remember right you have 4 DDR3 slots, but you might want to download and run cpu-z or open the side of the case to verify. http://www.cpuid.com/softwares/cpu-z.html
the memory tab will tell you what you currently have installed, per stick, and how many slots you have total.