Ok so I think all these chips should be ok. I had intermittent issues with every chip while going through them, some not detecting at all. I went back to Horun's suggestion of cleaning and gave them a good clean with contact cleaner (and not normally something I'd do but a quick once-over with some very fine grit sandpaper I use for polishing in other hobbies).
Seems that did the trick. The overall artifacts I believe now were due to some chips not detecting at all and therefore not having a proper configuration when all chips were installed. Then when i tried just two chips, I didn't realize they needed to be in U4/U6, so same full screen artifacts.
Now I've got all 6 sockets populated and no artifacts. 1024x768 true color works with the 4mb total.
Thanks again for everyone's help!