Matt-H
here I come to the rescue again. Get the PCMCIA flash memory, its definitely worth is as it is the only option you have for upgrading the Amiga 600, (unless you have or can find an Apollo 630 or Viper 630)
Try getting a Apple Newton Flash card. I have one and it works great. It makes your 600 feel more usefull. I do recommend thoug that if you get a trapdoor 1 meg ChipRAM expansion first though and then the PCMCIA, and get the largest one you can. I suspect that an 8meg Flash might work but not sure and it has to be 5v read and 5v write I believe.
I have a 1meg Flash from an Apple Newton on mine and I love it! gonna get a bigger one soon. You can boot Workbench superfast if you install it in one of these!