Why are you searching for internal strength? Why is it missing from your Aikido training? Why are you going outside your art to find it? When I read the threads about this training it makes me wonder what you are lacking that you have to go find it.
Once when I was joined in the conversation I was told I don't have it because one of my students doesn't have it. If you asked me about that student I would agree. His heart was not in it. Aikido training lets your inner strength out. You don't have to go to an expert to find it.
Aikido training for me is a whole practice�he development of correct feeling is just part of the process in becoming what Aikido is molding me into. Are you missing the point in your impatience to be the strongest person alive?
What was Gozo Shioda missing when he went outside the art? What about Koichi Tohei? Kisshomaru, for that matter, was made to go outside the art by his own father, for sword training. It seems to be more the rule than the exception.
Aren't you always trying to improve your training? It's not a matter of trying to be the strongest person alive, it's a matter of a training method that is just...better.
I haven't trained with the others, but I highly recommend Dan's classes if you get the opportunity. I think you'll find that he's not quite the soulless fighting machine you seem to be thinking of