I agree completely on the business class machines for two reasons- durability and parts. I've repaired too many Acers and Gateways for customers to be able to recommend one. The Dell OptiPlexes and HP dc-series desktops are both more durable. Plus, if any part breaks on my OptiPlex 745, I can run to the back room and have it within 10 minutes.

Four slots is definitely the way to go. My OptiPlex 745 is running 4x1GB sticks, but I could go to 4x2GB sticks for 8GB of RAM. For me, though, 4GB is plenty.

For Windows 8.1, try a free program called Classic Shell. It'll give you a Windows 7-like Start Menu. But, that really defeats the point of having Windows 8. Most refurbishers (Me included) will recommend Windows 7. It really is the next XP- the one OS that won't be topped for a long time.

Even though I handle the same type of machines as the stores with "Off Lease" machines, check the specs. A lot of those machines are churned out is mass with low RAM and slower CPUs. There are well-equipped ones out there, but most of the "specials" seem to have 2GB of RAM and 80GB hard drives. If you pay to upgrade the RAM and HDD, you may spend more than you would to choose the nicer machine.

A tip for you- when they say 2GB of RAM, you're probably getting 4 512MB sticks. To go to 4GB, you have to purchase 4 sticks, not 2.

Just my $.02