Adobe Photoshop uses OpenCL acceleration. Brush strokes, zoom and move tools, blur filters and countless others are accelerated on the GPU. A 4 core I7 4770k with a HD 7770 or R7 260X or a GT 650TI is faster and runs Photoshop smoother than a 6 core I7 4930k with a GT520/GT610/HD6450. It is really worth it to invest in a mid tier GPU. I do a lot of 8K textures in Photoshop and if I turn off GPU acceleration it gets really hard and sluggish to navigate after I throw in a dozen or more layers. Also AMD video cards are a lot better at OpenCL for the same price than their nVidia counterparts.
As far as Illustrator goes, if you really wish to do complex projects you need descend raw 2D performance. AMD is again better than nVidia in this case.
In the end, I got to this build which hovers under 1500 Canadian $. You can always change the case, but make sure it fits an ATX motherboard and cooler height of at least 160 mm. Cheers and good luck.
PCPartPicker part list /
Price breakdown by merchant /
Benchmarks
CPU: Intel Core i7-4770K 3.5GHz Quad-Core Processor ($359.79 @ DirectCanada)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($32.50 @ DirectCanada)
Motherboard: Asus Z87-PLUS ATX LGA1150 Motherboard ($151.50 @ Vuugo)
Memory: Corsair Vengeance LP 32GB (4 x 8GB) DDR3-1600 Memory ($370.65 @ DirectCanada)
Storage: Samsung 840 Pro Series 128GB 2.5" Solid State Disk ($135.98 @ Newegg Canada)
Storage: Seagate Constellation CS ISE 2TB 3.5" 7200RPM Internal Hard Drive ($139.75 @ Vuugo)
Video Card: Asus Radeon R7 260X 2GB Video Card ($159.75 @ Vuugo)
Case: Cooler Master HAF 912 ATX Mid Tower Case ($57.99 @ NCIX)
Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply ($55.99 @ NCIX)
Total: $1463.90
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-02-26 09:31 EST-0500)
As far as the Quadro cards go - for Photoshop, you are better of with a consumer grade card from AMD. The Quadro cards are good when you have dedicated CUDA support such as in Nuke or use the nVidia PhysX plug-in in Autodesk Maya/Max.