Other Hardware Devices Releated with the HTPC ver. 1
If you selected an case without an psu you have to buy one. Heroichi or Enermax are two excellent choices. Try to buy an psu over 300watts.
2) Cpu Cooler
Try to find an copper based cooler that costs a little more but it is silent and keeps cooler the cpu. Gigabyte , Coolermaster and Zalman are three good solutions.
Keep in mind that not all the cases can fit any cooler so look out for the correct size of the cooler.
You should use 512 mb ram or above. If you have enought money try to buy Geil , Crosair or Crucial memory sticks since tehy generally have lower latency.
4) Hard disk
Try to buy an hard sisk 200gb and above. This will be capable enought for movies, mp3 etc... Two good solutions are Maxtor and Western Digital. If your motherboard support serial ata hard disks then it is highly recommended to buy serial ata hard disk.
For small cases it is recommended to use a low end graphics card like Radeon X300 or Nvidia GEForce 6200. If you need a better card then use one Radeon X600 or Geforce 6600. However power users can put any vga card in an ATX desktop Htpc case.
6) DVD Recorder
I recommend an pioneer dvd recorder or a toshiba. The prices are pretty low so there are a lot of alternatives here. Since a DVD recorder costs 50$ max there is no need of CD ROM reader or DVD ROM reader.
7) Capture card
Tv cards like Pinnacle and Hauppauge are really good solutions. An also good alternative solution is the Terratec Cinergy.
Take a look at the minimum requirements of every tv card. Also investigate for the recorded quality of the video.
If you are not satisfied with the onboard sound card's quality then a good choice is Creative Sound Blaster Audigy 4 for movies or games. About people who need to do analog to digital conversion or the opposite, the recommended card is Creative Sound Blaster X-Fi Xtreme.