40MB should be fine for most things on a 68k. Upping it to 68 or 128 would allow you to run more things at once, but how often are you going to do that? The only things that really benefit from large amounts of RAM on a 68k Mac are Photoshop or video editing software.
Take a look at MacIPRPi. Run it on a Pi and boom you've got an AppleShare server that you can connect to from your Quadra, and any modern machine. Makes it super easy to download stuff from the Garden on your modern computer and access those files on your Quadra.
MacIP protocol
www.macip.net