1. What is the most reliable and quick-delivery source?
No way to tell. Be sure to look for concealed damage immediately because they are very fragile in transit.
2. If we get a unit like the Maestro that is equipped for whirlpool, etc. is it possible to plumb to an accessible location and cap things for the future addition of options?
It depends on what you plan to add. Some items do not require additional facilities other than an electric outlet. Others may not be readily retrofitted. Be sure you can add them later if it is something you might want.
3. Home Depot quotes $632.26 for the Lasco 60ACTS, Lowes quotes $711. for the AquaGlass 626034B. Which would you choose and why?
Which do you like better. You have to live with it, we don't.
4. We are willing to pay a little over $1,000. for a real quality and attractive unit like the Maestro with all of the extra features and future expandability -- is it worth it?
Again, that is a personal choice you have to make.
5. Any other gotcha's we should watch for?
Be prepared to have at least one defect with the unit. It may not happen, but it is also not rare.