It takes about 2 hours to build a system from putting in the parts to having Windows running, not that much time. If you want a pre-built one, just about any brand is fine, but you will be paying about %30 more for same speed as if you bought the parts yourself. What you may want to do is get a used business tower with an i5 or i7 CPU for about $300 and then buy a GTX 750 Ti video card or it. Just make sure the power supply is 300 watts or higher. Will be faster than any "gaming" pre-built system for under $600 and will cost about $400.