I have never built a HTP before , and built my firt one last week, and it was so easy and runs like a dream.
There are a few things to condsider when creating a HTPC what is it primary use eg are you going to game on it? or just use it for Online content and recording and watching TV?
You dont want to go for some power hungry hot and heavy beast, otherwise you may as well stick with a standard desktop PC.
Sata drive- I would ditch the Sammy 7200 rpm for a Sammy Samsung EcoGreen F1 DT 1TB - 32MB 1,000GB SATA II 5,400rpm
http://www.skycomp.com.au/product.aspx?id=107881 Saves on Noise and runs super cool, plus it should last a lot longer seeing as its only 5400 rpm.
Motherboard - GIGABYTE GA-MA78GM-S2H
http://www.skycomp.com.au/product.aspx?id=98474 is a no brainer, it supports AM2+ and DDR2 and has Optical In and out plus DTS ect and the other plus is it has HDMI. HDMI is important if your like me and are going to double your HTPC as a Blueray 1080PHD player.
Why go AMD over Intel? AMD Phenoms are cheap, DDR2 is cheap and the Onboard ATI graphics on AMD boards are a lot better for High Def content than the current Intel versions.
CPU - I notice you have not mentioned, This is a great buy AMD Phenom Quad-Core X4 9350 2.0GHz 4MB Cache, 65W Socket AM2+
http://www.skycomp.com.au/product.aspx?id=122895 , while not as fast as Intel, it sure makes up for it as a HTPC CPU. It runs at 65 Watts, this means it doesnt use much power and is super cool, and it runs that cool that you can use a passive heatsink with it and be safe in knowing that its not goping to burn up, and the best thing about this is that it doesnt need a Monster of a cooler that is going to generate disstracting noise while watching TV,. It has more than enough power and then some for HD content.
Ram- Doesnt really matter 2 much I had a spare 4GB of DDR2 floating around so I went with Vista 64 bits for my HTPC to use the full 4gb, but 2GB is more than enough for day to day use. If you do decide to get 4gb you will need a 64 bit version of Vista to utilize the full memory.
Case - The Silverstone looks like a awsome case its personal preferance here, I myself went with a Antec Fusion with remote, while this case is cheap, I could have got a lot more exspensive one but I just didnt see the point, I rather spend the money elsewere.
PSU- I purchase the seperate PSU
http://www.skycomp.com.au/product.aspx?id=123384 this PSU is desighned for the HTPC in mind it has active PFC, this saves on wasted power, and I cant even hear the thing run, but any PSU you decide on will do the job, anything over 430 watts is overkill and will be wasted and allso generate more noise. A modular PSU maybe something to look into as well.
TV card - Hauppauge HVR2200MCE great choice, I got one as well and its great, I cant compare it against another Model or make because this has been my first TV card.
Video Card - you dont need one, unless you want to play modern games on the HTPC like Cryses ect.
DVD rom - I would look at future proofing your system and going with a Blueray player/DVD burner they are relativley cheap, you can get a Blueray Player for under $180 and this will allow you to move to the next gen Format sooner rather than later.Make sure it is Sata, this way you dont have crappy Ribbon cable all over your nice case
Wireless Networking WiFi - This is something else you should be looking at You will need a wirless Network PCI card and allso a Wireless Modem Router, you really will need to think about this because without it you are not reaping the benefits of having a HTPC, you can update your Guide, surf the net ect with one, you will need Wifi to connect to the net if you have a ICETV subscription. If you do go Wifi you should look into a Draft 802.11n Compliant Modem Router and PCI card, 802.11b and 802.11g standards are 2 slow for HD content over Wifi and the n Standard is the future with Wireless speeds of up to 270mbps.
These are what I went with
http://www.netgear.co.uk/rangemaxnex...ter_dg834n.php and
http://www.netgear.co.uk/rangemaxnex...ter_wn311b.php
These may not be the best suggestions for you, but these are what I went with when I built my sytem 2 weeks ago, I wanted a system that could play Blueray @ 1080p have HDMI and good onboard sound. I allso wanted to watch and record TV, use the internet, and have a machine that was easy on the power usage and super quite, I think with whats available the AMD option was the way to go.
My next step is to purchase a reciever/amp so I can run the HTPC to a Hometheater 5.1 or 7.1 setup and get the true Blueray experiance, but for now I am taking it one step at a time, and if you pick your product carefully you should be able to enjoy your HTPC experiance for years to come.