I'm also running a Dart return pump on a 225, and honestly think it may be too much flow through the sump for a return pump. Works great, don't get me wrong, but it's a lot of flow.
Give us some more details about your setup. How many drains (and sizes) do you have going to the sump, and how many return lines (and sizes) are you running from the sump? This missing information may make the decision much easier.