To address the gfx settings reset:

Make another wow install folder for the clones and make a dynamic link to first install for the data, cach and interface folders. Search the MKlink command for Vista users. This will allow you to set the clones at min gfx and lower AA if you choose.

The extra ram will really help out. Toss it in to help out overall performance. You will find a lot of debate on ram and 32/64 bit performance if you search around these forums.

If you are running 2 monitors then using one video card is prefered. Once again there is much debate to found about one vs two video cards in these forums. I yanked a video card on my machine and plug 2 monitors into one card.

You can also see some performance gains by turning down the AA for your primary instance. Going from 8x to 4x alone showed a huge performance gain for me. I currently run all instances with the same settings but the clone windows are very small.

Good luck.