PC Spec for AVCHD Editing Using Sony Vegas Pro 10 : Sony Vegas basics

Hi
Can someone help with guiding me on a spec for a PC that will give me a pleasant experience (and short/reasonable render times etc) for HD video using Sony Vegas Pro 10.

I am looking at the following:

Case COOLERMASTER SILEO 500 QUIET MID TOWER CASE
Processor (CPU) Intel® Core™i7-2600 Quad Core (3.40GHz, 8MB Cache) + HD Graphics
Motherboard ASUS® P8Z68-V LX: USB 3.0, SATA 6GBs, ATI®CrossFireX
Memory (RAM) 8GB SAMSUNG DUAL-DDR3 1333MHz (2 X 4GB)
Graphics Card 1GB NVIDIA GEFORCE GT 520 - DVI,HDMI,VGA - 3D Vision Ready
Memory - 1st Hard Disk 1TB WD CAVIAR BLACK WD1002FAEX, SATA 6 Gb/s, 64MB CACHE (7200rpm)
2nd Hard Disk NONE
RAID NONE
SSD CACHE DRIVE NONE
1st DVD/BLU-RAY Drive 12x BLU-RAY RE-WRITER DRIVE, 16x DVD ±R/±RW (£79)
Memory Card Reader INTERNAL 52 IN 1 CARD READER (XD, MS, CF, SD, etc) + 1 x USB 2.0 PORT
Power Supply 450W Quiet 80 PLUS Dual Rail PSU + 120mm Case Fan (£29)
Processor Cooling SUPER QUIET 22dBA TRIPLE COPPER HEATPIPE INTEL CPU COOLER (£19)
Fan Controller NONE
Sound Card ONBOARD 6 CHANNEL (5.1) HIGH DEF AUDIO (AS STANDARD)
Network Facilities 10/100/1000 GIGABIT LAN PORT - AS STANDARD ON ALL PCs
USB Options 2 PORT USB 3.0 INTERNAL PCI EXPRESS CARD

The total cost of this is around £838 or $1,340

I edit video for fun - just the normal sort of stuff, family holidays, events etc up to about 30 mins in length although I do like to be 'creative' with FX's etc.

My question is also whether I should look at a higher spec Intel i7 six core which with further upgrade etc takes me up to about $1700. How much additional speed/benefit will this give? Should I strive for this if I can afford it?

As a newbie, the other thing I am struggling to grasp is (i) the benefit of a second HDD and whether SSD and or the benefit of RAID?

Sorry if this is a bit long winded but the more I research the internet the more challenging it becomes given the different advice that seems to be out there. I want to get this purchase right both from a performance and price perspective so any advice would be gratefully received.

Thanks