You guys are discussing the most unimportant aspects of a 600+ Km anti-sub missile.
The reason why ASuMs have low range is because more range is simply unnecessary, that's the range subs normally get detected from. But if our ASuM has more range, it means we are planning on making the missile highly networked, aka, CEC. This will entirely change the way ASW is conducted. All we have to do is park a few frigates/destroyers in some strategic locations and offboard sensors can cue torpedoes to any part of the Arabian Sea or Bay of Bengal in a matter of few tens of minutes.
This requires some really serious networking capabilities though, something that doesn't exist today in any country. For example, a destroyer 300Km away from an ASW helicopter 100m over surface will not be able to see each other. This will require MALE/HALE UAVs, MPA, satellites etc to transfer data between the helicopter and destroyer, so one can imagine the amount of background work that's happening when multiple nodes are involved and the target is constantly on the move and requires periodic real time updates.
There's another more kickass method. Laser satellites. Laser satellites actually carry a lidar, which is capable of penetrating water up to a certain depth, enough for ASW.
But this tech is quite sometime away.