These T5500's were once top-of-the-line performance PCs costing thousands of dollars, and have now reached the price general consumers can afford. They are built like tanks and have plenty of drive bays and slots for expansion, can handle a huge amount of memory (especially if you get one with a second processor on a riser card), and have power supplies large enough to support all of that expansion. The tool-free design is one of the best chassis designs I have ever worked on from a expansion and maintenance point-of-view. Even though T5500's are a decade or two old, they are still relevant in today's computing world. The limiting factors are the onboard PCI 2.0 bus, SATA II and USB 2.0 controllers. Add a decent SATA III controller and USB 3 card -- neither of which is very expensive -- and you are good to go for another decade. I own three of these beasts in various configurations. The only parts I have had to replace are two CMOS batteries, and one fan for the second CPU riser memory.