Help Me Build A High-End Windows 7 PC

My main PC stopped working today.  No matter what I do the network adaptor on my Abit IP35-Pro motherboard won’t work.  I’ve been toying with building a new high-end Windows 7 rig for a while and given that my PC is my livelihood I want to build a new Windows 7 machine fast.  If I can salvage any of the parts from my current system, I will use them to upgrade other PCs in my household.

My current spec is below:

• Q6600 LGA775
• Abit IP35Pro Motherboard
• 4GB Ram
• ATI HD 4650
• X-Fi soundcard
• Swiftech CPU&GPU watercooling
• 600w Seasonic S12-600 PSU
• 400GB HDD
• Gigabyte case

I’m planning  on keeping the PSU, GPU, HDD and soundcard so I need:

• A new fast HDD to run the OS – should I get a SSD?  Which one?
• A new CPU and motherboard.  I’m hoping to keep my LGA775 watercooling block, but getting a different size isn’t a problem -it just adds $50 to the cost (hassle removing as well, but I can handle)
• Lots of new RAM – how much should I get?  I don’t play games but I do a lot of encoding/decoding, multitasking etc
• Will I need a more powerful PSU?

My total budget is £1000/$1600 so this should buy me a very good spec machine.  Suggestions on what I should buy and why below please!  Also suggestions for a cheap LGA775 motherboard please just in case I can’t salvage the Abit IP35Pro.

Update 20/12: I’ve ordered my parts and they should arrive on Tuesday – thanks to everyone who made suggestions. Here’s the spec for the new machine (new parts in bold):

• Case: Gigabyte Aurora
• PSU: Corsair TX 650W
• CPU: Intel Core i7 920 2.66Ghz pre-overclocked to 4.00GHz ;-)
• Motherboard: Gigabyte EX58-UD5
• RAM: Corsair XMS3 6GB (3x2GB)
• GPU: HD4650
• Soundcard: X-fi Xtreme Music
• OS HDD: 80GB Intel X25-M SSD
• 2nd HDD: 400GB SATA II
• Cooler: Noctua NH-U12P SE1366 (ditching my Swiftech watercooling as the pumps are about to go/it’s getting very noisy)
• Monitors: Samsung T220 22-inch x2

I can’t wait to put this baby together!

My old Abit IP35 Pro motherboard completely died last night, so I ordered a Gigabyte GA-EG41MF-US2H motherboard to build a new machine for my wife (she has a very,very old laptop at the moment) from what was left of my old PC:

• CPU: Q6600
• PSU: Seasonic S12-600
• Motherboard: Gigabyte GA-EG41MF-US2H to go in an old Foxcon microATX case
• RAM: 4GB Ram
• HDD: 400GB SATA II(canibalised from my WHS)
• Cooler: stock
• Monitor: Samsung T220 22-inch