Pics above are before and after, if that wasn't obvious.
While ordering parts for a machine for my children this week, I threw in a couple extras to upgrade the first machine I built a little over a year go. This is the first time I've done anything since building that machine so it's not my first or second build, I'm calling it build 1.5.
I added an ssd for the OS and game installs, upgraded my case from an Antec Three Hundred to a Corsair 300R (can't say enough about this improvement*), and "downgraded" my PSU form the Antec Gamer 750 (non modular) to the Seasonic m12 II 620 (modular). I also removed the optical drive for my kids machine since I've never used it since my initial install of Windows 7.
I'm pretty stoked on the outcome TBH. The SSD is obviously a big upgrade in speed. The PSU is still plenty sufficient and much neater, which along with the case make for a much much cleaner build as you can see from the pics.
*A Note to New Builders About the Cases. I went with the Antec Three Hundred with my first build because it was moderately priced and had literally thousands of stellar reviews. When I was putting it together I couldn't believe how much of a pain it was to work with, especially for cable management (I know some people have some amazing builds in them, but it seems more for people who are cutting out holes and customizing it, not first time builder style).
When I originally ordered this stuff, I got the R300 case for my kids' build and the Antec One to upgrade mine. It was definitely much better than the Antec Three Hundred but it also had it's little annoyances (usb 3 connector doesn't fit through closest hole to the back ect, minor but annoying). Then finally I went to put in my gigabyte hd6870 (last step of course) and uh... didn't fit. Fortunately I already had the 300R for my kids so I decided to throw my rig in there.
Everything about the Corsair 300R is awesome. It was so much easier installing and managing cables and everything in this machine. IMHO it's so worth the extra $30 for a first time or new builder, even if you're not planning on upgrading or working on it more, and if you are... then it's absolutely worth it. Caveat: I haven't built in any other cases so maybe there are other cases with comparable features in the same price range or lower, but I couldn't find them.