I honestly wouldn't worry about the CPU all that much. It's going to be a while before you run into any CPU contention with your FX-4170. Most of the heavy lifting gets done by the GPU nowadays. I know people who have Core 2 Quad systems that can run Battlefield 4 acceptably just because they have a decent video card. When it comes to gaming I try to cycle out my CPU every 3-5 years and my video card every 2 years (though with my current setup the latter might get bumped to 3 years...we'll see). I doubt I'll consider upgrading my i7-3770 until mid-2016 unless I get a really kickass deal on a Skylake (the planned successor to Haswell) CPU after they come out this coming year.
I used to use a modular power supply until I realized that I was actually using most of the cables. :x Thankfully, I've scaled back a bit since then, so I could probably make good use of one of them now (I went from 1 SSD and 6 HDDs to 2 SSDs and 2 HDDs this year), so maybe when I get my next PSU. I don't have a side-window, so I'm not too worried about aesthetics, and I'm able to route the cables in my case so that they don't interfere with airflow.
Speaking of cabling, the case can make a pretty big difference. I'm not sure which one you're using, but I'm using a CM Storm Trooper and it has some pretty nice cable management options, including the ability to run cables behind the motherboard tray (giving you a reason to pop off the right case cover) and several points to feed in zip ties.
And yes, you need an SSD, preferably paired with a UEFI-compatible motherboard and a version of Windows that supports EFI boot (Windows 8/8.1 support it and Windows 10 will as well). UEFI is essentially a rewrite of the classic, older-than-Spectere BIOS system, and can drastically reduce boot times. Coupled with an SSD, you can end up seeing boot times that are ludicrously fast. My laptop (ASUS ROG G750 with a Corsair MX100 SSD) cold boots in literally a few seconds.
As far as prices go, I'd say that DDR4 is going to start becoming affordable to normal enthusiasts (rather than cutting edge enthusiasts) by mid-2015. We'll also be seeing a lot of lower-end parts springing up due to product binning (i.e. Intel or AMD fabricates a chip that can't run at its intended clock speed, so they sell it as a lower-end model), so that's going to push prices on the core components down a bit. Speaking of binning, NVIDIA should also have the 900 series more or less filled out by that point (and AMD will be doing the same, I'm sure), so we're going to start seeing a lot more replacements for lower- to mid-range current-generation GPUs as well. 2015 is shaping up to be a very fun year to be a hardware enthusiast!