@Dtl yeah, we can't resolve individual sources as yet, but 'loud' binaries are likely to be resolved once several more years of data is collected. I'm not sure M31 has more than 1 SMBH though? An example of one I am keeping my eye out for is OJ287 - eccentric orbit, short period, radiating GWs and we have an EM counterpart signal we can try to fit with it as well!