Buy a Buick!
In all seriousness, I've yet to swap out any spring/coilover suspension component that had a softer, more supple ride than stock. I've had lowering springs and coilovers (one or the other) on Celica's, WRX's, STi's, Lexus', BMW's... and none of them had a more comfortable ride than stock. Maybe you'll find a perfect combination for the 370, but I'm guessing stock is going to be close to as soft of a ride as you are going to get. Good luck in your search though.