I agree to keep using whatever makes you happy, amsoil certainly has some very nice products, and you seem to have an excellent plan. However, for the sake of discussion:
Amsoil, has some great products, some OK products and some that are merely OK and overpriced (like their oil filters). Amsoil's dealer system allows some absolute morons to tarnish the entire organization (claiming that mobil 1 is group III based, outrageous OCI claims, etc). Amsoil's own marketing hypes tests (4-ball wear) that make their products look great, but have minimal relvance to actual conditions, espicially compared to performance on used oil analysis.
I'd say that Mobil products are the only syn oils availble over the counter worth using. In the Mobil 1 line, I'd say that the 10W30, 15W50, and 5W40 are excellent, and the others are slightly less impressive.
I don't trust Castrol enough to feel entirely comfortable with their only common syn oil, German 0W30.
I think that Redline, Royal Purple and Neo are overpriced, hard to find, and offer virtually no performance advantages, at least in engine oils.