Flow from a Dart for a the return might be a lot your sump.
If going CL, as mentioned, consider something for water motion (eg. OM 4-way and there's one FS here). As for CL themselves, I'm running one with a Dart and happy with it, but might want to read through this
thread by Niloc16. Has a nice well thought out tank but noise ended up being an issue with the CL. My tank is in my family room and though don't even think of pump noise during the day (TV, kids etc) it is noticeable at night when everyones in bed and I want to read a book by the tank.
Salt, 1 bucket isn't going to last long.
Joe Reefer's comment is something to seriously consider. Having a fishroom behind or even a basement sump eases maintenance like you wouldn't believe.
Also, hope you've had a chance to visit people with large tanks. As much research I did when planning and running a 75g, to actually see peoples setups helps a lot.