Ah, that is true! The 1.67GHz never came out and was bumped to 1.83GHz. I remember reading about that, I believe. People who pre-ordered the former were automatically upgraded to the 1.83GHz.
I just Google searched the entry to refresh my memory (no pun intended) and found this:
[http://www.designedinca.com/macs/macbook_pro/jan2006/1670-15>
You may have something there. Not necessarily that we can soup up the high-res PowerBooks, but the design process leading up to the MacBook Pros.
Great thinking! Thinking different, ha ha! =)
I've read that too. In fact, here on these forums I believe. Someone asked about that. Getting the 2GB module, since those weren't available when the PowerBook 1.67GHz came out. I've read it is feasible (though I don't know if anyone tried it, because they didn't want to buy it and find it not work), but at that point, you can only put one 2GB module in and any other module, from 256 to 2GB wouldn't work since the maximum is 2GB for the machine.
P.S. (I asked a similar question a few years ago with the PowerMac G4 Dual, if it could have four 1GB modules to max out at 4GB, even though the PowerMac maxes out at 2GB. The idea comes from, where else? The Pismo, which was officially supported a 512MB--or was it 768MB?--maximum, but people found it could take 1GB later down the road, with no hacking or alterations necessary).