Just when you thought there was nothing left to say on the subject, I may have stumbled upon a solution to drive the Xenarc in native 800x480 using the onboard video without CMOS/ROM mods or PowerStrip.
I'm not sure what happened, but it seems the DDC channel to the monitor is not working (the com channel between the MOBO and the Monitor - I2C bus). Therefore, the MOBO cannot detect the monitor connected. I set the resolution to 800x600 and the Xenarc detects it as 800x480. I then recal'd the Touch Screen to only use the top 800x480.
I then set RR to 800x480 and presto - I have a solution!
I also had to set the CMOS video to enable both CRT and TV. I have the latest 4 in one drivers loaded.
To see if the DDC had anything to do with what I was seeing, I connected the Xenarc to another PC and set the resolution to 800x600. The display detected it as 800x600.
There is one down side. Sometimes the Xenarc cannot sync at all and goes into off mode.
I can't say this potential solution is conclusive by any stretch, and I don't want to suggest that people hack into their DDC channel, but if an experienced user feels comfortable openning one of the DDC pins to see what happens, please post your results.