To upgrade or not is really a question only you can answer.
If you want to run the latest OS, applications, and plugins... upgrading in a ~3-5 year window (depending on your performance needs) makes sense.
It's hard to beat Intel CPUs.
All the following can be set and locked at 4.4GHz... which provides a lot of DSP processing.
- 4790k (4 cores - dual channel DDR4)
- 6700k (4 cores - dual-channel DDR4
- 5820k (6 cores - quad-channel DDR4)
If you're doing video work (lots of rendering - especially 3D rendering), you can't throw enough machine at the situation. Animated 3D Rendering is far more demanding on the CPU than multi-track audio.
If you do 3D Rendering professionally (Cinema 4D, etc), I'd recommend at least two (if not more) networked machines to setup Team Render. Cinema 4D makes this easy... and it cuts render times down to a manageable time-frame. With a single machine, rendering 30 second spots of high-res 3D video can take over 24-hours.
The 5820k (Haswell-E) is essentially the 5930k with 28 PCIe lanes instead of 40.
For most folks (unless you plan to run dual video cards), 28 PCIe lanes is sufficient.
Socket 2011-3 runs a little on the warm side, so you'll want high performance cooling to run cool/quiet at 4.4Gz
The 6700k (Skylake) is the latest i7 quad-core CPU... using DDR4.
Runs a bit cooler than Haswell.
4790k (Haswell) is still a great performing i7 quad-core CPU.
Performance is just a shade less than the 6700k at the same clock-speed.
Though slightly higher in cost... the 4790k, 6700k, and 5820k outperform any current AMD model.