Current system build:
CPU: Intel Q9650 3G quad core. I was strictly AMD for years, but recently I've learned to value reliability over price. That is not to say AMD is unreliable, I have several older computers and two notebook computers with AMD processors that are very reliable. I just think a combination of an Intel processor and motherboard should be very reliable. Also, this is the highest price point that I wish to pursue.
HSF: Xigmatek Dark knight. I was set on using the stock Intel HSF until I checked the core temps after trans-coding video for about 20 minutes. So, with the help of several members here, I picked the dark knight. I has provided sufficient cooling for the cores a 95% or higher sustains CPU loads. I didn't want to mount something this heavy or bulky on the motherboard, but the mount with the bracket on the back side of the motherboard is very solid. I'm very happy with it.
Motherboard: Intel DP45SG also, in combination with the Intel processor, reliability at the highest price point I consider reasonable.
RAM: I've used Micron RAM for many builds with excellent reliability, but went with 4 Corsair 2G "sticks" figuring on performance as well as reliability, but an unknown factor for me. So far, excellent results.
Hard drive: Maxtor 1TB SATA and a Seagate 1TB SATA. Both were on sale for less than an $100, a reasonable price. I have had very good reliability with Maxtor in the past, and the Seagate is basically the same drive. In fact, the drives are identical except for the name and a couple digits in the long model numbers. If I remember correctly, Maxtor owns Seagate. I store most of my files on network attached storage, but I like to have at least two drives with a fair amount of room for processing video, reading from one drive and writing to the other. Then the files to the NAS; the computer drives are "working space."
DVD/CD RW: Pioneer DVR-216D SATA for performance and reliability. Price is low enough not to be a major factor with this component, at least for me. I've had excellent performance with Pioneer drives. I've used a couple of them to the point that I was amazed they still worked. I did look into Blue Ray, but I think pricing still needs to drop significantly before it becomes a value to me.
Power supply: Exclusively PC power and cooling. Excellent quality, great voltage regulation, and reasonable pricing. I've posted here also that I've seen an Antec power supply in a server that was so hot I couldn't touch it because the fan failed. The server never failed, so I have to say that I favor Antec as well. I've seen cheap power supplys go out in flames or usually, just stop working under the same conditions.
Case: Cooler Master elite 335. Good pricing. 120mm intake fan capable, and 120mm fan exhaust. Intake duct over CPU, although with the dark knight HSF that I'm using, the duct was removed. Screw-less quick mounts for all the drive bays, plus drive bays from top to bottom. In my overclocking days I build systems that sounded like a fleet of B52 bombers. These days I appreciate quiet computers. I have grown very fond of good 120mm fans for their quiet efficiency.
Video display adapter: Currently, EVGA Nvidia GeForce 9600 GSO 512. I'm still learning about performance display adapters, I usually don't go for much performance. Normally if I can get native resolution on a display I'm happy, but I wanted some gaming performance for this system. I am now considering a pair of adapters powered with ATI HD 4870 GPUs, perhaps 512 ram and a crossfire bridge. These choices are mostly influenced by the motherboard chipset capabilities and choosing a reasonable ATI GPU performance point.
Monitor: Acer V223W. Excellent quality display at an amazing price. Also an older NEC 1940CX that I got on sale a while back. I really like the combination of 16:9 22" for my main center display and a 19" 4:3 secondary on the side. Most of the time I only use the 22" but when processing or capturing video it's nice to run that in the 19" so my main display is free for other tasks. It's also handy to be able to go full screen with 16:9 or 4:3 (depending upon the video aspect ratio) to check for video artifacts.
In the past I was very into overclocking, but with current computer performance and component pricing I have lost interest in trying to squeeze more performance out of the components. Reliability and the pursuit of reliability has become a big influence.