Also forgot to mention - The Magna Carta was supposed to have a Panoptic system, but it got cut when it failed to fit once the JD was researched. 2000tons is a huge system, and there have been plenty of times I have missed it, particularly against a certain spoiler.
Panoptic Search System m1 (1) GPS 6400 Range 161.9m km Resolution 10
With a size four (technology 8 ) passive EM detection sensor you will detect this ship at a distance of 200mkm. A dedicated sensor ship will detect it at billions of kilometres, not to mention ground based listening stations that will pick it up from more or less any ware in a solar system.
In general I view it as a waste of time to develop such systems since they only draw the attention too whomever are using it. Any ship small enough to be detected can generally either outrun the ship using it or other smaller ships can slip in under the resolution and engage with missiles anyway. The ship using the expensive sensor will also be target number one. I no longer put anything with a bigger resolution of 5 on any capital ships any more since the power output that will be detected by other higher resolutions is so high. Larger resolutions are only fitted to smaller and fast scout ships that can avoid enemy capital ships and who can rarely be engaged before I have had time to launch my missiles, probably even from a safe distance without even being detected. Not to mention the very expensive research I need to dedicate for such huge projects.
In a setting such as mine investing such resources into a huge active scanner locked into a specific resolution is a waste of resources since the only thing someone else need is to have bombers of many different sizes, and strangely enough that is what usually happens in my campaigns. Bombers and FAC usually range from 125-1000t... smaller ships generally deploy their payload closer and larger at bigger distances. It becomes too research heavy to build large sensors to catch them all, that is why passive sensors are much more important to me.
I would rather build a huge thermal sensor to detect the above ships you mentioned earlier, which also might let your main ship be undetected if you are lucky. Throw out a net of surveillance ships around your fleet with huge passive and large EM sensors. It is much easier and cheaper to research a maximum size passive sensor than an active one and in my opinion you get better use of them too. Then build a scout ship with a resolution XX active scanner to paint that target once they are detected. With this method you can send in your surveillance ship and detect the enemy long before they know you are there and attack them with whatever resources you need to get the job done.
The absolutely most important ships in most of my arsenal are my surveillance ships, usually about 3000-4000t with only passive sensor systems. Usually a size 30 Thermal and a size 10 EM sensor, their engines are often with as much reduced thermal as possible and then they also run slow to avoid being detected by ground or ship based detection systems. Each fleet get as many surveillance ships as I think they will need, depending on how many there are. When cloaking is researched then my surveillance ships are the first to be fitted with one.
In addition to these surveillance ships I also deploy smaller reconnaissance ships that the fleet keep in their hangar bays, these usually range from 500-1000t and also get a decent EM and a very large thermal sensor. These are generally the advanced picket of any task-force, or they can be sent of to search remote places as needed. The smaller 500t get stationed in more regular ships such as destroyer leaders while the larger are stationed in utility carriers. These utility carriers are mainly the same size as destroyers and can operate with such task forces.