What Should I Upgrade? Mid-Line PC

Hey, so I built my computer about a year ago, and I have really gotten into the tech community on Youtube and stuff like that.  I love it.  Looking back on my build, I realize that I made a lot of mistakes and I should have put some more money into things that I didn't.  My main computer usage is Gaming.  I play all kinds of games from Super Meat Boy to BF4.  I also do some graphic design work, which comes with the occasional 3D render.  Multitasking is very important to me, I like to work on a design project and watch a video, maybe play a big game while watching Netflix.  I just wanted some feedback from people that know more than me about what I should upgrade.

Here are the specs and peripherals (I know it's pretty ugly):

MSI A78M-E35 Micro ATX Motherboard

AMD Athlon X4 760k 3.8GHz Quad Core Processor

ASUS HD7770-2GD5 - 2GB GPU

8GB of Ballistix Tactical Ram

Corsair CX500 PSU

64 GB Adata SSD (Only has about 9 GB Free)

500 GB WD Green Drive

be quiet! Pure Rock CPU Cooler

4x 120mm Cooler Master Sleeve Bearing Fans

1TB WD "My Passport" External Drive

Raidmax Cobra (The cheapest, ugliest case in the world)

My peripherals are fine, I have a K70 and a Deathadder.  I run 2 ASUS Monitors, and just some USB speakers.  I feel like it's time to upgrade and I just want to know what I should upgrade first and to what products.  I want to spend maybe $600 in upgrades IN TOTAL.  Thanks!

 

 

 

 

 

The build isn't actually too bad.  Your peripherals look like they're pretty high quality stuff, so I'll focus on the build.

Grab a better GPU.  You would see the biggest performance increase here.  A GTX 970 or a R9 290 (although the R9 290 might be a little bit close for your power supply) would be a good option.

Grab a CPU cooler and see if you can overclock the CPU.  I'd highly recommend a Hyper 212 Plus/Evo if your case can fit it.  If not, look into one of the various 120mm all-in-one watercoolers.  Graphic design/3D work can be hard on the CPU in some occasions.