We have 3 replicas running, one NW 6.5SP8 and two OES2SP3 (eDir 8.8 SP6). These 3 servers are 32bit.

I'm about to test NCS in the lab (we've not used it before) and see on page 50 (4.6.3) of "clus_admin_lx.pdf" that eDir 8.8.7 is required for managing cluster objects.

Is it okay if we keep our existing replicas and not yet add a replica to our OES11SP1 servers?

I interpret that requirement as saying that we need to manage cluster objects using iManager on one of our OES11 SP1 servers which run eDir 8.8.7. No replica required, correct?