@ig316b, As best as I can remember at least some of the SCS’s came with port plugs. I’m not sure if those models were optimized for use with or without. Often times used models are missing them. I don’t remember if the port plugs were offered for the PCS’s. I believe the earlier SCS’s came with 2’nd order crossover which are not as time coherent as Thiel’s models’ that featured 1st order crossovers. Generally the lower the monitors go; the better. Keep in mind there are other parameters considered when designing between ported and sealed boxes.
@jwei Bass in rooms can be problematic. Room treatment for bass issues can be cumbersome. Reducing reliance on room treatment can be less expensive, and less intrusive. I suspect placing the subwoofers for the best room fit first, and then dealing with the spacing / time alignment with the appropriate monitors with now less intrusive DSP might be best.