My experience is just the opposite. Off the shelf computers frequently don't allow for multiple internal HD's, upgrading RAM, adequate cooling, and being VERY quiet, etc. While today's gaming computers may have better graphics cards, they may still lack features I want for photography.I applaud you for having the skills, knowledge and drive to build your own computer, but I’m surprised that you’re not able to find one available suited for photo editing in the marketplace. I’m certainly no geek, but from my view seem to be a number of commercially available units that work quite well for most post processing tasks, and serve the professional community well. Personally, I always like to consider warranties and long term support whenever I purchase a new unit, but then I readily admit that I don’t have the skills to do it all myself. In any event, best of luck in whatever you decide to do.
I don't have the skills to build my own computer, but by working with Puget Computer Systems I can get the perfect machine for my needs today and the future, while still getting superb warranty coverage and support for long after the custom build. Puget Computer Systems is a brick and mortar business in the state of Washington and when I call a knowledgeable person answers the phone and helps me.
Yes, it's a bit more expensive than an off the shelf computer, but it lasts me for 8-10 years - including upgrades. In fact, after the storms pass, I will open it up, clean 'er up a bit, install a new (pre-wired) internal HD, copy data to the new HD from 3 old internal HD's, and increase my storage capacity while reducing the number of drives in the case.