Well, summoning isn't that bad, but you shouldn't look at the brutes. By the books a Hecantoncheire has 52HD and CR57.
If you can summon those, research the ability to get Ancient Prismatic Dragons instead. It's also CR 57, but has 68HD and CL 32 - that way, you summon 10 casters that are almost as good as you yourself are.

May I ask what your goal in doing that is? That might help us find better strategies.

Finally, you should take a minute or so to ponder the consequences of using stuff like the locate city bomb or fell drain wightpocalypse. Some DMs don't like players pulling that kind of stunt - perhaps you should ask out of game where your DM draws the line, so you don't do something he ins't prepared to deal with and you get a "Rocks fall, everyone dies". (Unless that is what you wish to achieve, but that would be kind of immature).