FWIW... Checking relative horsepower of CPUs on CPU-Mark and relating to new Dell T3400 vs. T3500... 1. If you want to stay low cost, T3400 is the way to go. 2. If you want to spend about $1100, then the T3500 with Xeon W3520 is better deal than the equivalent T3400 with upgraded CPU. 3. The W3503 and W3505 Xeons on the T3500 are rather whimpy... especially when considering the cost. If you go with T3500, looks like a no brainer to get the W3520 CPU.... faster ones OK too, if you don't mind paying to show off. T3400 has x38 mobo with 2, PCIEx16 + 3 PCI slots. T3500 has x58 mobo with 2, PCIEx16 + 2 PCI slots
The base units of T3400 were a terrific deal when they first came out. I think Dell should have lowered the price more than they have, but still a good deal.... especially if purchased off of Dell Outlet. Usual savings on Outlet purchase is about $150 vs. from retail site. Sometimes, however, there are super-good deals... but they disappear quickly as many are keeping an eye out for them.
In this day and age, I think in the hardware world planning for a 5-year out is a bit far. I think the IT department of most large corporations wouldn't wait that long to refresh their inventory. 3 years, perhaps. Of course now we are in a bad economy, that may change. There is always this "next thing" just around the corner, but it requires this (new) and that (new). Software applications drive hardware requirements. It all depends on your applications, of course. Some shops are still happily using their 486 with Windows 3.1. Hey if it does the job, why change? Despite being an IT person (formerly anyway), I personally prefer to stay on the trailing edge of technology to take advantage of the rapid price erosion (especially in hardware). e.g. I use 4 low-end Compaq desktops as my work-horses to drive my charting software. $350 each (bought at different times). I know they might be bottom of the line in today's standard, but since they do the job I need, why not? In another 2 years, I might pick up another bottom of the line box at that time for $350. All depends of what you want it for, so...