Memory Cpmpatibilty for IIgs Board 670-0025-A

I've got a IIgs w/ROM1 and with a memory expansion board in the slot. Part# of apple card is 670-0025-A. Bank (0?) memory chips were soldered directly to the board and the remaining 3 banks had empty sockets.

All was working well until I wanted to play an old game (Shadow Gate by Icom) and the system reported out of memory. So, I went on e-bay to purchase what I thought was the correct type of memory chips. The 16-pin DIPs I purchased read:

GS I23W Korea
GM71256- 12

I visited one of the old usenet posts and found out how to set the two jumpers. I tried this and get one of a couple of errors:

"Sorry, system error $00FF occured while trying to run the next application."

"Fatal system error 0308"

The errors do not appear when I set the jumpers back to factory and I assume, disables the newly added memory. This tells me that the memory is not compatible. Can I get a second opinion on that?

Also, if my assumption is correct, what is the correct type of part that I do need and what is a good source to find this stuff. If I'd be better off getting a different type of memory board, I'd be open to that suggestion too.

-Dono