@ Stephen. That dip in the middle of the saddle is very desirable. That should not be the dicisive point to buy another saddle. The saddle doesn't have to be horizontal either, that is why they are adjustable. Some people need the nose down, some up. If you tip the saddle forward, you may end up sliding forward and end up with your seat bones out of the support seatin gon the nose and putting also more weight on your wrists that will have to try to push you back. I do my gross adjustment like Julian suggests, then I put the bike in the trainer and ride for several hours over a couple of weeks. Without the distractions of the road, my body tells me what I need to adjust. At the bottom of the stroke, your leg should be "almost" fully extended but not quite. At about 10 degree angle (180-10) of bend, the knee starts what is called locking mechanism which include a medial rotation of the calves (this wears out the knee). That is why we don't need to use the muscles when we are standing. The knees are locked. If you extend more than the 10 degree mark, you start the locking of the knee and then you need to use another muscle, to unlock. This mucle, the popliteus, is weak and fatiges quickly, also slows you down as the big muscles can't operate untill the knees unlock, and looking knees also makes cycling less efficient. If you saddle is too high you will have pain in the back of the knee, the popliteus muscle, if it is too low, pain in the front of the knee (relying on the ACL to press down). Also if it is too high, your pelvis will have to tilt to each side as you reach down. This is really bad. Your pelvis should set square on your seat bones without rocking sideways.
And finally, the height of the handlebar should be set after the saddle is fit and is not a meassure of where to put the saddle. When the saddle is fit right, Then you adjust the handlebar, for aero dynamic purposes it will be lower than the saddle. The body should form a tripode with some weight resting on the seatbones, and part on the handlebars and most of it on the pedals, where it can be used. A saddle is not a chair for you to put your weight on. As you pedal, you will lightly touch the saddle with your seatbones.