I recently upgraded my work computer and spent a lot of time selecting from the different options available to get a good value for my money. In the hopes that someone will find this useful, here are the components I selected and why. I bought my parts from Newegg and have provided direct product links.
Start with an excellent MicroATX Motherboard. DFI makes a high quality product and this is the best motherboard I have ever owned. Incredible amount of BIOS options.
DFI LanParty JR X58-T3H6 – $200
Next, select the fastest Intel processor at a reasonable price. Also overclockable if you’re into that.
I actually bought 6GB OCZ DDR3 1333 Memory. However, it is out of stock.
Even though I bought a different brand, here are the things to consider. Find memory with the highest speed rating and lowest latency within your budget. I also like G.Skill brand. I wanted 6GB at around $100, but I also had limited clearance in my case so didn’t want heat spreaders. I chose DDR3 1333 with slightly better timings (7 7 7 18) over DDR3 1600 with average timings (9 9 9 24). There is also DDR3 1600 with better timings (8 8 8 21) but it has tall heat spreaders. I wanted to keep it slim. Keep in mind that often you will have to adjust BIOS settings to take advantage of faster ram.
Because I got a MicroATX motherboard, I went with a MicroATX case which is about half the heigh of a standard Mini-Tower case. You can get even smaller cases, but I wanted one with a 120mm rear exhaust fan to minimize the noise. There is also a bit more interior space than an even smaller case.
Make sure to pay attention to the size of the power supply. If you go too low it may not power your system reliably and will reduce the life of the power supply (and could cause random lockups or reboots). If you go too high then the power supply will be less efficient at lower wattages and you’ll be wasting electricity most of the time. The best thing to do is a rough calculation based on the max wattage of all the parts and go 10-20% higher.
Depending on your case, you may have to be careful about the size of your video card. I also wanted dual-dvi output for two monitors at 1920×1080 and modest power draw. I went with a relatively slim single slot Radeon HD 4670. I also like the fan that exhausts the hot air out of the case.
1.5TB Hard Drive. I chose the Seagate Barracuda, even though a lot of people online claim firmware issues with it. I haven’t had a single problem. You could get two of them and run them RAID 0 (striped) for performance or RAID 1 (mirrored) in case one fails.
Pick whatever DVD-RW drive is on sale with the features you want (dual-layer, LightScribe). I like LITE-ON or LG brand. I chose a black one because it matches the color of the case.
If you need a new monitor, you can get 23″ LCD’s for under $200. Make sure it has at least DVI input, and supports 1080P. Most of them are 1920×1200 which gives you a little more vertical space, but I chose one that supported true 1080P 1920×1080. I really like Samsung brand but it tends to be more expensive. Other good ones are ASUS, Acer, and Viewsonic. I got two 21.5″ LCD’s for dual-display, but most people only need one 23″.
Total Price: $900 without monitor or $1100 with monitor.
If you’re upgrading, you may be able to reuse the old hard drive, video card, dvd drive, or case (and power supply), depending on how old they are. If the parts are too old, it makes sense to buy new ones because the old parts could severly hurt the performance of the new machine.
If you want a beefier video card, you could upgrade that and go with a smaller hard drive or a smaller monitor.
You could also shave off around $200 by going with a Core 2 Quad CPU and Motherboard instead of Core i7. You would also likely have to change the memory to DDR2 instead of DDR3. However, even though the Core i7 is only 4 cores, it has HyperThreading enabled which means it essentially runs like it has 8 cores. That would be good if you use VMware or run a lot of CPU intensive programs at once.