Hi there,
Do you have a budget in mind?
I believe Autocad makes use of
Nvidia Quadro graphics cards (which tend to be rather expensive compared to their gaming "geforce" cousins). You can go for the cheaper option of a gaming graphics card - but if you will be using autocad extensively (and professionally) then I think opting for a quadro does make sense. To give you an idea of price, a Quadro 2000 card (very similar to a geforce GTS 450) costs ~£360.
As for CPUs, the new Quad core Sandy Bridge Processors are the ones to look for. Pound-for-pound the i5 2500K is the best one to get, but if you have a large budget then the £70 more expensive i7 2600K is worth a look - its main benefit over the 2500K is hyperthreading, which will boost performance in heavily multithreaded applications.
Also, considering the applcations you mention are generally pretty CPU-heavy, overclocking the CPU will yield some performance increases. If you just buy a P67 board and a decent CPU cooler then you can do this yourself (it is pretty simple to do with the K series CPUs). If you don't feel so confident then you can buy a
pre-overclocked bundle from OCUK.
Adding an SSD (so long as your budget can bear it) would also be a good move - as it does make loading any files and general usage of the PC feel so much quicker.
As for RAM, DDR3 prices are pretty low at the moment - you can pick up 16GB (4x4GB) for less than £160 (just under £10 per GB), two of
these kits would be great.
For monitors, it really depends on budget - without knowing this I will just recommend a nice quality, good value screen that will work well for your uses. This
Dell U2311H is a really nice bit of kit and uses a high quality IPS panel.
