I tried using the defaults, and there were still problems. I'm not sure if I'm quite ready to accept that it's a bad video card just yet, as this 7800 GS was the result of an RMA of another 7800 GS that was having similar problems, and had some bad onboard memory. Aside from the artifacting, this card runs at more normal specs that the RMA'd card, such as GPU temp and default memory clock speeds. Besides, I believe they stress test all RMA replacements before shipping them out.
That being said, I am also not yet ready to rule out the possibility that EVGA flubbed up and replaced an RMA'd bad card with another bad card, but I would like to eliminate all other possibilities before trying to talk EVGA into taking it back (as well as spending the money to ship it back out to California).