You'd have to specify an IP address on the Mac's ethernet port (which I assume is currently unused) and on the empeg, as there will be no facility for automatic address assignment. And I'd suggest going ahead and specifying the empeg's address within jEmplode rather than relying on broadcast scans working. (It might work with broadcasts, but I don't know how jEmplode determines the correct broadcast address and it might not select it properly, but since there's no detriment in specifying it, you might as well.)

I can see how there might be some problems with getting the Mac's ethernet port's autonegotiation of speed and duplexity working right, but you should be able to overcome those without much effort if they do crop up.