New to PRE and need feedback on my system build

Question

I played around with the trial version on my old computer and decided to go ahead and purchase PRE 9 and PSE 9 together. I have built a few PC's in my day and recently completed my current build running my purchased software. I was hoping that I could get some feedback on what I have and what I might change to get better performance. PRE is very jittery when scrolling through content and playing back the timeline. Sometimes I don't even see a transition. I am new to video editing in general and capture in HD with my Canon HF S100, so I am planning on editing in HD as well. Sorry for the NoBo question, but my machine smokes until I fire up PRE. I may be using the application incorrectly, but I am assuming that my low end video card, is an area of concern/bottleneck. I don't want to blow $800 on a Quadro 4000 if it won't make a huge difference, but I assume it will. Thanks in advance for any and all help.
High level build
MoBo - ASUS P6X58D Premium LGA 1366 Intel X58 SATA 6Gb/s USB 3.0 ATX Intel Motherboard
PSW - CORSAIR HX Series CMPSU-620HX 620W ATX12V v2.2 and EPS12V 2.91 SLI Certified
Proc - Intel Core i7-950 Bloomfield 3.06GHz LGA 1366 130W Quad-Core Processor
Mem - 12GB Mushkin Enhanced Redline 240-Pin DDR3 SDRAM
Drives
     OS - Crucial RealSSD C300
     Media - Western Digital VelociRaptor WD6000HLHX 600GB 10000 RPM SATA 6.0Gb
OS - Windows 7 x64 SP1
Video - NVIDIA GeForce 9500 GT
Detailed DxDiag output below.
System Information
Time of this report: 2/27/2011, 19:30:14
Operating System: Windows 7 Ultimate 64-bit (6.1, Build 7601) Service Pack 1 (7601.win7sp1_rtm.101119-1850)
Language: English (Regional Setting: English)
System Manufacturer: System manufacturer
System Model: System Product Name
BIOS: BIOS Date: 05/25/10 14:57:23 Ver: 08.00.15
Processor: Intel(R) Core(TM) i7 CPU         950  @ 3.07GHz (8 CPUs), ~3.1GHz
Memory: 12288MB RAM
Available OS Memory: 12280MB RAM
Page File: 8908MB used, 15647MB available
Windows Dir: C:\Windows
DirectX Version: DirectX 11
DX Setup Parameters: Not found
User DPI Setting: Using System DPI
System DPI Setting: 96 DPI (100 percent)
DWM DPI Scaling: Disabled
DxDiag Version: 6.01.7601.17514 32bit Unicode
Display Devices
Card name: NVIDIA GeForce 9500 GT
Manufacturer: NVIDIA
Chip type: GeForce 9500 GT
DAC type: Integrated RAMDAC
Display Memory: 4069 MB
Dedicated Memory: 997 MB
Shared Memory: 3071 MB
Current Mode: 1920 x 1080 (32 bit) (60Hz)
Monitor Name: Generic PnP Monitor
Monitor Model: ASUS VH242
Monitor Id: ACI24FA
Native Mode: 1920 x 1080(p) (60.000Hz)
Output Type: DVI
Driver Name: nvd3dumx.dll,nvwgf2umx.dll,nvwgf2umx.dll,nvd3dum,nvwgf2um,nvwgf2um
Driver File Version: 8.17.0012.5896 (English)
Driver Version: 8.17.12.5896
DDI Version: 10
Driver Model: WDDM 1.1
Driver Attributes: Final Retail
Driver Date/Size: 7/10/2010 04:38:00, 12471400 bytes
WHQL Logo'd: n/a
WHQL Date Stamp: n/a
Driver Strong Name: oem3.inf:NVIDIA_SetA_Devices.NTamd64.6.1:Section003:8.17.12.5896:pci\ven_10de&dev_0640
Rank Of Driver: 00E62001
Video Accel: ModeMPEG2_A ModeMPEG2_C ModeVC1_C ModeWMV9_C
D3D9 Overlay: Supported
DXVA-HD: Supported
DDraw Status: Enabled
D3D Status: Enabled
AGP Status: Enabled

Answer 1

This ARTICLE will give you some tips on your I/O sub-system setup for video-editing.
As for the Scratch Disks, think of those as the "working files," that PrE produces and needs to edit video. Part of those will be the Media Cache, where you will have the CFA (Conformed Audio) files, the PEK files for Waveform Display, etc. For a bit of background on Conforming, see this ARTICLE.
Now, for ultimate performance, one would want to spread the I/O load over as many discs, as is possible. The OS and programs accessing the HDD is a given, but you have already segregated them onto C:\. Then, one has the Scratch Disks, which also require quite a bit of access. The media is accessed often for many operations, and then there is the need to Export/Share. In a perfect world, one would allocate a separate HDD for each of those operations, with one caveat: when one has finished a Project, there will then be the cleanup of the files. If one has spread the Project over multiple physical HDD's, they must go to each, and do the cleanup. OTOH, and at the sacrifice of ultimate spead with I/O access, if one has placed their Project into a root folder, say [Project Name], and then accepted the default location for the Scratch Disks, for Same As Project, all they have to do is Delete that Project Name root folder, and everything else comes with it. As I migrate Projects between computers, I locate everything in a Project Name root folder on an external, and then everything is below that folder structure. For media, I leave my Assets on an NAS, and just Copy over what I need to the various media sub-folders, like Video, Stills, Music, Audio, etc. I give up performance, but have everything that I need to move the Project about, and cleanup is easy. In my case, each external has a permanent drive letter assignment in the OS of each computer, so that drive Z:\ is always Z:\ on each computer, and regardless of what else might be plugged-in to that computer. Makes life simple for me.
Hope that this helps.
Good luck,
Hunt