System plan: powerful, silent, upgradeable

I've been visiting Tom's Hardware for years, but just now I've created a user account and this is my very first post here.

I'm planning on buying a new computer before year's end to replace my current Intel Core 2 Duo based system. I think I'm quite confident on what to buy, but perhaps I'm making some (obvious) mistakes I didn't think of and am wondering if there's anything you'd do differently.

Beforehand, here are the key thoughts while compiling the list of components:
- System needs to be upgradeable for years to come (i.e. add memory, upgrade CPU, etc.)
- System silence is absolute key
- The smaller the case, the better; good looks important, too
- No overclocking - ever
- I have no TV; system is my TV (with analog cable input)
- Must be able to run OS X if required in the future
- Usage purpose: audio/video editing, TV/movie/video watching, web/mail/office, torrents, music listening
- Budget: < 1000 euros (for new parts; I will migrate some old parts; see below)

The challenge thus is to get the system as small and silent as possible, yet still having brute force power.

Ok, here we go for the new parts:
- Case: Lian Li PC-A05NB
- PSU: Silverstone ST45NF (fanless)
- Mainboard: Gigabyte GA-EX58-UD3R
- CPU: Intel Core i7 920
- CPU cooling: Scythe Katana 3
- Memory: Corsair XMS3 TR3X6G1333C9 (3x2GB=6GB)
- HDD: Western Digital Caviar Green WD15EADS (1.5TB)
- TV Card: Hauppauge WinTV HVR-1700 Media Center Kit

In the Netherlands (where I live) I would be able to purchase the new parts in various stores for a total of 896 euros.

Here's what's migrating:
- HDD: OCZ Vertex Turbo (30GB)
- HDD: Western Digital Caviar Green WD10EADS (1.0TB)
- GPU: NVIDIA GeForce 9400GT (1GB)
- Audio: M-Audio Delta 44
- Optical: NEC ND-3500AG
- Monitor: BenQ FP241W 24" (P-MVA)
- OS: Windows 7 Ultimate x64 UK
- Keyboard, Mouse, Speakers, etc.

The two main worries I currently have are CPU cooling and memory related. Firstly, I'm not sure if the Scythe Katana 3 would actually fit the Lian-Li case. And secondly, I'm not sure if I've selected the absolute right memory. Sure, it'll be compatible and it'll work, but I'm not sure if I selected the fasted memory for that price. I have no clue if I should match FSB with memory clocks or not - I don't have good knowledge about that, unfortunately.

Well, that's it. Thanks for reading and I'm looking forward to reading your respected opinions.

Thanks Silmarunya. The HDD indeed is pretty slow compared to many other disks, but I think it is fast enough to store and load documents, video, audio, downloads, etc.

The reason I think I can make this trade-off is that I have a 30 GB OCZ Vertex SSD for Windows, apps and swap file. If there were no SSD, I certainly wouldn't have considered the Green series.

Surely, if anyone believes the Green series is no good for general storage as well, I'd like to hear about that.