I just went to my LFS and got one they had with more GPH than my old one had. I don't have a brand to recommend, perhaps others will chime in?
I would suggest checking the GPH recommended for the chiller, then get the next size up from that. Adding a chiller, tubing, valving, etc, to your 2 tank system should make upsizing GPH a good idea. Thinking about having 2 tanks, with possibly different temperature issues, could mean designing some type of valving system to distribute intake and return flow as needed to maintain each tank at your desired temp level. Those PVC valves work petty well and are cheap too.
Post some pics when you get the chiller plumbed in and working-sounds like an interesting project!