It really depends on what you do with your computer. I had a Core 2 Quad system that was perfectly fine for me in 2008, but as I dabble further in HD video editing, I dropped money on a new system a month or two ago. Now I can preview effects in real-time, and the rendering time is so much faster. Likewise, working with photos from my Canon T2i. The ability to chuck 24gb of memory in the system doesn't hurt either, and SSDs? I actually put my 4-year old computer on Craigslist for free because it seemed pretty useless to me after upgrading to this new system.

I'm looking forward to what kind of technology will be available in 2016.