Well, 8 units of 16 megabytes (MB) will give you the maximum of 128 MB and 8 units of 4 megabytes gives you about 32 MB. You can throw in the maximum it can support, but be sure you do two things:
1.) Have the system extension file called "Mode32" placed inside the Extensions folder within the System Folder on the hard drive, and
2.) The more RAM you install (above 32 MB) will cause the SE/30 to take a bit longer to boot; this is perfectly normal. Just remember that.
If you don't want to install "Mode32", you can buy a spare ROM SIMM out of a Mac IIfx, IIci or IIsi, and replace the SE/30s' ROM SIMM with that. The IIfx, IIci and IIsi ROM SIMMs are "32-bit clean", whereas the SE/30 is not. The SE/30 has up to 24-bit data addressing, which is why this model, out of the box, couldn't support more than 8 MB without the "Mode32", enough though it can take up to 128 MB.
As far as where to get RAM,
http://www.pcmemorystore.com sells 16MB sticks for about $30 USD each. Another couple of places to try are eBay and Amazon.
73s de Phreakout. :rambo: