AFAIK, there is no difference between 512Ke & Plus that would prevent software from running except for the RAM. Since you can easily turn a Plus into a 512Ke, you have no need to worry about upgrading to a Plus.
However, if you are like me, you want to keep that original case design. Look for a DOVE MacSnap SCSI upgrades which turn up from time to time on eBay and add SCSI to that 512Ke. You can also add RAM, but that would defeat your desire to run Megaroids.