Expansion potential.. Also, in some lines, different cooling design, e.g. Hp Z line: HP Z4xx is the same as HP Z6xx, except for the second chip capability - even if I use only one chip, the whole chassis is better cooled, sound insulation is also better, different PSU design, RAM, storage options, and extra card slots. For one, the Dell T3620 line has extra storage configuration options (RAID, etc). There are many other small differences, if you look into the specs. Sometimes we need them, sometimes we need them not..
I learnt to stay away from buying consumer box store computers. They die out a few months out of warranty. Checkout craiglist and ebay for commercial workstations off lease. Purchase top-of-line workstations, desktop and laptop for about .10 on the dollar.
I helped a family member who used a Dell Dimension for their business. They used it everyday and depended on it. I spent many hours improving it, quadrupling the RAM, tweaking their Windows, changing out the hard drive for a larger faster one, oiling the single fan inside, backing it up, etc... It went from a very slow desktop to being noticeably faster and quicker. ALL of the 12 larger/taller Dell Dimension's motherboard capacitors leaked or bloated upwards. The system started freezing up in Windows. It wasn't worth the effort to replace the capacitors so I helped them buy another computer. They ended up giving the Dell Dimension away to a small store which takes any donations. I wrote a note telling the store about the problem and how a young person could replace the capacitors and have a working computer. They probably threw the Dell away. Here is a picture of some of the Dell Dimension's leaking capacitors. The leaking capacitors are the tall black and light blue ones. ALL 12 OF THEM LEAKED OR BLOATED UPWARDS. The capacitor on the far right bloated upwards. This is why I don't buy prebuilt computers, especially used ones. You never know what you're getting. I have been building my own computers for many years. I usually buy the highest performing components available. This way I don't have to build a new PC for a long time. Building, even only buying, a new computer is very time consuming. In addition, you must install your own software, tweak it, tweak Windows. This is my current computer. See only the first and last minute. I built it, tweaked Windows, installed all the software, etc...
All this talk about computers made me just want to upgrade my five-year old 15" HP laptop to a slightly newer and better one. a 17" Dell workstation laptop. Just purchased one on eBay for around $300
You may not know or recall, but originally the Dell Dimensions had IBM motherboards. At some point, they switched to Foxconn... and not too long thereafter discontinued the Dimension line. Maybe that's all related? Maybe you got some of the early Foxconn mobos? Maybe yours came from an early bad batch? Nevertheless, not a problem today.
Just get a Lenovo Thincentre M9x Tiny for less than $200 from Ebay. Some comes with 3 years onsite warranty. This little devil can drive a 4k monitor or a total of 5 Monitors 1080p. and spend the $ on a monitor that will be gentle on your cornea.
Spec says no wifi and bluetooth. Space permitting, a refurb professional HP or Dell with intel quad core xeon workstation for multiple trading platform and office apps, goes for about the same price or less. Imagine with weight of all the cables would be more than the unit. But if it works for you, go for it. Send a picture of it fully operational with 4 monitors running a few apps.
Thinkcentre comes with bluetooth and Wifi (usb/wifi dongle is only a few bucks) I have a M93p Tiny i5 attached behind a 4k monitor (MicroBoard 43") + a dell monitor. This provide a clean desk and floor set-up , no cable web. I only have the power cable dangling from the computer. It can run and display more app than I can use or read. What sold me on the M93p is the small form factor, Thinkcentre reallibility on site service, integrated Intel Hd graphic , displayport. Here is the spec http://psref.lenovo.com/syspool/Sys/PDF/ThinkCentre/ThinkCentre M93 M93p Tiny/M93 M93P Tiny.pdf