Hello....Liveaboards are a great way to go. I can only answer to Palau. I have been on the Palau Aggressor a couple of times and it is a very nice operation. They only take up to 18 divers on a trip. They have 7 and 10 day charters, plus they also operate the Dancer Fleet in the area which might give an additional option. It is a very nice boat - redone in 2010. I had the chance to go through it as they were bringing it back from its refit and they have done a very nice job with this boat. I think both of these boats would hit all the boxes you mentioned up there, except muck diving. Palau has some good macro opportunities, but just not your muck diving. Mandarin Fish lake is one of my favorite dive sites - especially at dusk when they are mating.
German Channel is great for Mantas, and Blue Corner is a fabulous dive for seeing sharks and large schools of fish. They use reef hooks so that you can stay on the wall and watch the encounter for awhile. There is current in Palau - some of it very easy and other times it can be pretty fast. But then that is where you use the reef hooks and hook in and enjoy.
There are also some good wrecks to dive on in Palau. Plus you have Jellyfish Lake - which is a MUST.
Good luck with your choices and have fun - Pam
Edited by DiverPam, 26 March 2013 - 08:53 AM.