Computer's are NOT moving as Moore's Law has postulated in the recent past. 'Speed' has outgrown need for most. A 5 year old computer is now useable for almost anything. This was NOT the case in 2008, one made in 2003 wasn't equipped to handle 2008 OS's and tasks, as OS load grew (more RAM and CPU power needed) as did program (features and size). Today's systems are much faster, and the adherence to Moore's Law is not holding true. Well, it might be if you consider die size and transistors in the MFG. process, but NOT is the realization of faster systems.
WHS, you have an XPS 8300, I have an XPS 435T (3 1/2 years old), the predecessor to the 9000, 8300, and 8500 my wife has (6 months old). My wife's machine was the basic, no upgrades. Mine was upgraded to a better video card. Still, today, both on W8 they perform about the same. Both have 8GB's of RAM and SSD's. Actually my OLD ATI HD4870 video card out performs here HD7550 (Dell OEM) video card, and my machine therefore had a higher Windows Experience. Our older computer, and old Dell 8100 and here Sony at one time were only a year apart, a 1.6Ghz Intel Duo-Core2 for here and my P4 Hyperthreaded, and mine was decidedly slower. Today, not the case, and for anything we throw at these computers, they can easily handle it. Even MS FS X with full options on, still smooth, although my video card looks 'cleaner'.
There are not many killer apps for the home user today that tax many machines. For the average person, anything the big box stores sell will suit them well.