On the desktop for AutoCAD, the best entry-level workstation card is the AMD FirePro V4900 for $160
The laptop equivalent of the V4900 from HP can be found on ebay for around $200. I'll try to look up a link/model number for you. Forget everything you listed and focus on the card.
Workstation cards have accelerators/drivers with advanced geometry/math capabilities. The advantages in this relates to your screen re-generation as you zoom in and out of various portions of your line drawing. The bigger the file, the better the regeneration with the workstation card.
An SSD will boot the laptop faster, and launch your app more quickly. More RAMs help, but only to the extent it limits hits on your page file. With 4GB you should be fine, but 2x4GB fast RAMs are really inexpensive these days.
A Trinity APU quad-core should be an excellent option to build upon, even prior to the workstation card. I put *AutoCAD OpenCL* in my search engine, and the first listing was FirePro drivers.
The **SIMD Engine Array** on the Trinity APU contains *Turks* cores. The same graphics engine on the FirePro V4900 ...