It's a solid build and outside of replacing your Hard drive with an SSD, the main power is going to come from your GPU (graphics card). Most benchmarks are used with an i7 at a substantial speed and most all games will only utilize 4 cores and the i5 is a top contender in the CPU arena. So your CPU is solid but it cannot be overclocked, you should spring for an i5-2500K (The K stands for unlocked chip) which is about the same price. And since Ivy Bridge (3000 series) is really only a die shrink with some slight changes in light of Sandy Bridge (2000 series) the performance is right around the same. That chip can overclock like a beast, so that should never be a limit on your FPS for quite some time.
So all in all it boils down to your GPU the 7870 which is a very capable chip, only a rung or 2 down from the 680 and 7970 crown holding realm. Overall the build is High-Mid range, but can be boosted by overlocking the chips so long as you get a "K" moniker on your Intel Chip, and the 7870 is a great overclocker as well.
I should note however that the build itself will be quite powerful when it comes down to gaming. If you are playing at 1080p resolution or aorund that you should be able to put a lot of bells and whistles on with fairly modest AA in most every game
Ok, I'm very new o this whole pc thing as I was a console gamer most of my life, but I understand the basics. So changing the CPU so I can overclock it (still a bit fuzzy as to how to do that) will increase my preformance and prolong the need to upgrade. I should point out that I'm not one of those people who needs every setting on ultra.
It's a solid rig, but if you have a microcenter nearby you head there, you can purchase a processor much cheaper. I would suggest an i5 3570k for roughly 180, I believe they still have them in stock. This will allow for overclocking in the future in a friendly format.
As for ASrock h77 I would suggest a z77 platform board from MSI at roughly the same price range. I don't trust ASRock at all. Look at
MSI Z77A-G41 LGA 1155 Intel Z77 HDMI SATA 6Gb/s USB 3.0 ATX Intel Motherboard with UEFI BIOS( 87.99 @Newegg)
As for the power supply I would suggest at that price range looking at an OCZ Stealth or ModXstream for roughly 60@Newegg. Modular and I've had experience with them not dying.
With the money saved by purchasing a processor at Micro Center you could afford a decent 32gb or 64gb SSD from newegg for a boot drive.
Also, I saw in your prices that you included final price with Rebate. They're notorious for taking 8-10 weeks to send rebates, as a forewarning.