If you go with pumps, yes you would use another SRC instead of the ZVC. There are lots of ways to skin this cat. If you use pumps or EBVs, you will not have the delay I have in switching on the house circs after switching on the P/S circs. I am using TACO heat motor zone valves, which use a resistance heater to warm a capsule of wax that expands and opens the valve. This heating process takes about 30-45 seconds, and is what causes the delay in the closing of the second end switch. Honestly, for a BB emmitter system, or really anything but an air:water HX, the few minutes of circulation with less than full temp water is unnoticeable and irrelevant. Build the system the way you feel comfortable. BTW - a "bad" zone valve head (actuator) can be changed out in 10 seconds without any plumbing to do. To change out the zone valve body, you could add unions on either side of each one, but the failure rate on the valve bodies is so low, and their life so long, I am not convinced it's worth the expense. I use the TACO 550 "gold" series, but if Steve has found issues with them, you might want to heed his warning.