Photoshop CS5, Video Editing, and Graphic Card choices???

Howdy Again,
I don't know if there is a Photoshop "STANDARD" or personal preference when it comes to shopping for a newer and faster graphics card, but I've been told I have a an underpowered one, which is GeForce 8600GT

Ok, I gathered all my info on my self-build. I assembled the Motherboard, CPU, GPU, and PSU, back in December of 2007. This upcoming December will mark the fifth anniversary of this rig, so it's been a few years, and will soon be time to do it all over again. (Can't wait)...nah, not really.

Keep in mind that I do not over clock, nor do I play games. I may watch a DVD, streaming video, capture and edit Video using Pinnacle Studio15 Ultimate, as well as use Photoshop CS5 intensively, and could use some stability overall. Something is causing my ''screen ghosting'' and ''Not Responding'' messages, some say it could be a graphic card failing.

Now knowing that my present card might contribute these issues, because of under-powerment, I'm seriously thinking of replacing it anyway. I was also told to look for the largest amount of CUDA CORES and make sure it's GDDR5.

NVIDIA told me that the QUATRO GPU is faster, and better suited than other cards, BUT they are VERY expensive. They are used for higher ended apps like CAD, etc.

So in my further confusion in choosing a new card, I see lots of video cards touting themselves as ''The weapon choice for gamers", etc.(Like the EVGA 660 Ti/PCI.E 3.0/2048MB GGDR5/1344 CUDA CORES, etc. for $300.00)


MY SPECS ~

MAINBOARD ~ MSI P35 Platinum/Intel P35 Chipset Crossfire 1395 (MS-7345)

POWER SUPPLY ~ Thermaltake "TOUGHPOWER" 700W ATX 12V - 2.2 & EPS 12V

CPU ~ Intel Core 2 Quad Q6600 2.40GHz (4 cpu's)

DISPLAY ~
EVGA Nvidia Geforce 8600GT (512MB) DDR2 128-Bit
(Memory clock speed 700MHz / HDCP Capable PCI-e / Total memory 4071MB (Driver version 8.17.12.9610) 2-29-12 DirectX11

MONITOR ~
20" Viewsonic - VX2035WN
60Hz ( Screen Res. 1280 x 800) True Color (32 Bit)

HARD DRIVES ~
Boot drive > WD SATAII - 74GB Raptor (10,000 rpms) 16MB > 4.6MS
Storage drive > WD SATAII - 2TB Green (7200 rpms)
Storage drive > WD SATAII - 500GB Caviar Blue (7200 rpms)
External drive > Seagate 3TB

OPERATING SYSTEM ~
Windows 7 Pro OEM (64 Bit) (6.1, Build 7601) SP1

BIOS ~
American Megatrends Inc. v.1.10 / 11/10/08
Current Bios version - 1.A0 / VGA Bios v. 60.84.41.00.06

MEMORY ~
8GB DDR2 / PC6400 / 800MHz (8192 MB) RAM
Available Physical memory - 6.12GB
Paging file > 4463MB Used, 11917MB Available

AUDIO ~
Realtek High Definition Onboard Audio

CASE ~ Coolermaster CM 690 / ATX

I'd like to spend between $150.00 - $250.00. Thanks!