Of course I then need an A600 or A1200 - but as they are cheap, I don't mind as much. I can always sell the A500, even thought I just got it! Should have thought about this a little more......
If you are planning to buy a new Amiga, then you should definitely go for the a1200 and not the a600. The stock a1200 comes with more ram as default and you can also buy a model which already includes a hard drive. The a1200 also has faster cpu, better graphic card and is more expandable than both the a500 and the a600.
What would be the best, is to get an already expanded a1200 with cdrom and such. I am sure you find a bunch of those on the ebay. The a4000 and a3000 is also a great choice, though probably more expensive than the a1200.
An a1200 is probably easier to get than a hd and ram upgrade for the a500 anyways, so i think you should definitely go with an a1200, a4000 or a3000.
You can however nicely use the a500 with octamed, as long as you dont use a bunch of big samples and use more than 4 audio channels.
Though a1200 is much more capable in most areas, but it should not stop you from using your a500 in the meantime. :-)