I'm looking to buy a new desktop system, mainly for internet, office and other regular activities. Most of the low end desktops I've seen go for around $300-$500. Now I went on craigslist and saw people selling gaming systems they built for around $500-$600 with significantly faster processors, gpus, etc. A few of them were relatively new and claimed to have active warranties for all the parts. So would there be any reason not to buy one of these "gaming" systems for everyday use? Would they produce a larger electricity bill even in normal use?