I used to roll my own all the time then I found it was more effective just to buy a base machine with right MB CPU combo and upgraded ..best deal was to find a return...usually more cost effective by a wide margin
but now switch to laptops as daily drive...
At that time a typical 286/12mhz AT with a 20mb hard drive, 2mb of RAM and an EGA video card & monitor was going for about $2k easily. I built the same thing for just over $900 at that time.
Somewhere around 1997/1998 I purchased parts to build two computers, which then sat --- for two years --- unbuilt because I didn't have the time to put them together. I ended up buying a Dell instead. Was happy with the first Dell, so after a year or so I bought a second.
I'll spare you the details of the horrors of that second system --- including the time the monitor sparked and caught fire while I was sitting at my desk in my home office. That happened less than 30 days after I purchased it and Dell was completely useless in addressing the issue or replacing the blown monitor. The computer also had its share of issuess (2 power supplies, memory going bad) which Dell was also useless in addressing.
I went back to building my own after that, mostly because I'd choose far better components than those used in mass produced PC's and because building my own isn't just cheaper, I actually have fun doing it.
Sent oldest son off to college in August with a new laptop and a gaming rig that I built for him, knowing he'd meet up with a bunch of gamers while away. Thankfully he keeps his grades up (he's in an Honors program at Western IL University) and to hear him tell it he has the fastest computer of anyone in his group and they always use his to stream via twitch when they're playing.
His gaming rig is a mini ITX format SFF PC with 16gb memory, dual SSD's, a GEForce GTX 970 video card, the latest Haswell i7 and is liquid cooled. It looks pretty darn good too in a Cooler Master Elite 130 SFF case with a 750 watt modular power supply by Corsair. I love building these things. His gaming rig is a beast. I'm building another one for myself this weekend. :-)