Upload & Sell: Off
these days GPU acceleration has become an integral part of many programs such as CS6, DxO and many more. this unloads the CPU for the heavy work and increases the speed at which things are done overall. so yes now a reasonably good quality video card will give your processing good kick. look at your programs, they will refer to things like open CL, CUDA and GPU acceleration in the preferences areas. it can make a big difference.
Agreed - but depending on what is being used... to a limited extent:
Photoshop: only assists in visual aspects with Open GL, few filters use MGE (at this time)
Premiere Pro: CUDA and OpenCL assets render in real time with MGE
More on CS6: http://forums.adobe.com/thread/979969
Personally, I spend that entire budget on a video card with 512 CUDA cores for video work and future compatibility.
It's getting there - but with a limited budget, GPU shouldn't be listed as a top contender. Again, it all depends on workflow: quantity/quality of photos, software and expectations.
Good CPU: $200-300
Base price (no GPU): $550 up to $900 for better parts. So yes, there is room for a low end video card if other parts are minimized. The question comes down to what offers the best bang for the buck... for each ones own needs.
[EDIT]: Better read (for CS6) here: http://www.adobe.com/content/dam/Adobe/en/products/creativesuite/production/cs6/pdfs/adobe-hardware-performance-whitepaper.pdf
Adobe Premiere Pro, After Effects, SpeedGrade, and Photoshop Extended each place unique demands on the major hardware components discussed above. Even different tasks performed inside the same software may vary these requirements drastically. In this section, we will state the basic system requirements for each software package, and then discuss specific demands and potential performance bottlenecks that may lead you to go beyond those basic requirements to optimize your own experience.