LOL, I have good news for you.
Not only is PPPoE good with NetBSD... it is probably best with NetBSD. That is because it does PPPoE in the kernel (basically it just means less moving stuff around in memory so slightly faster). It was for this very reason that I chose NetBSD for my router.
I am not sure of X on that hardware but I don't know why it wouldn't be possible. You should definitly try to get it working and not just resign yourself to never seeing it. I would try it on the faster machine (which is still fairly slow) just to see if it is possible.
You may not want to run it everyday... but it is nice to have around.