I was going to build my own machine and ran into problems getting the components to work together. I've been doing this for forty years and you know something? I'm sick of it. It's cheaper & easier to buy a new or refurb machine. In my case my former system was a 2 core system running Windows 7 Pro. I wanted at least 8Gb of ram with 4 cpu cores.I ordered the Dell Optiplex 990 tower offered an Intel i5 4 core cpu (3.2Gz), 8Gb of ddr3 ram, and a 2Tb hard drive.  I arrived very quickly, and I was surprised to find I was sent a Dell 3020 instead. The specs are mostly the same; It's still a Core i5 4 core cpu, but "only"  runs at 2.9Gz. 2 front panel USB ports on the front instead of 4, but there are two USB 3.0 ports on the back! Also, the 990 only has a Displayport on the back, while the 3020 has a Displayport and a regular VGA port as well. Nice option to have. I found a decent Displayport to DVI cable for about $8 on Amazon.All in all I'm pleased with the substitute as I get 2 USB 3 ports out of it!The only downside is the sound doesn't seem as good as my previous system, which featured 6 3.5mm jacks and a digital sound out. This has a single speaker out, mike in on the back. Nothing like a deal breaker, but music aficionados take note. USB digital speakers or a a PCIe sound card might be an option for you. Otherwise, it's a very good deal.