Hi Wayne et al,
Not been here for a while. Got your email about the proposed changes and I think it is a good idea to base he site on newer technology.
I've been looking into Drupal recently and it has certainly become quite a powerful CMS and with the usabilty changes due in version 7, I don't think there is another opensource CMS as powerful or flexible as Drupal.
That being said it is more of a bare framework and needs many modules installed to add features commonly found as default on other systems. Even a WYSIWYG editor is not natively built in and has to be added as a module.
But as you are familiar with coding It should not be too difficult for you to hand code any modules that don't already exist out there.
Legacy compatibility should not really be a problem as it is rare nowadays for someone to depend on a classic Amiga for web browsing. With the advent of cheap netbooks even moreso.
There was an offer on at Tesco Superstores last week where you could buy an Intel Atom 1.6Ghz powered Acer Netbook for £129 (129.00 GBP = $191.898 USD). :-o
Anyway back to the upgrade, Go for it I say. Drupal is no lightweight. It is used by some really high profile websites so you can't go wrong on the tech front.
Keep in mind the SEO aspect of this site though. Search engines have thousands of pages indexed and breaking the URL's could affect your rankings.
It might be a good idea to leave the original site where it is for archival purposes and put the new site in a folder. You could permanently redirect any traffic from the main homepage to the new on in it's folder and all references to the old URLs would remain intact.
In time you could migrate the content to the new platform and after it is re-indexed you could scrap the old one if required.
I haven't done this myself but have spoken to someone who has tried this method on a site of his.
Good luck with the upgrade. I'll be sure to follow it's progress.
See you around.
Gadget