Of the systems you've listed, all are expandable except the Bachmann. What some people do is start with a Bachmann, and then replace it as their needs grow. It's a more limited system than the others, which is reflected in the price.
Of the rest, it really comes down to personal preference, like walk-around vs. base station, or the size of the buttons on the throttles. They're all good products.
It takes an iron man to play with a toy iron horse.
Sounds like you have answered most of the questions and sounds like you have ruled out the Bachmann. The two big camps around here are Digitrax or NCE and both make good systems that can be integraded into the bigger more powerful systems if you decide to expand your empire.
I am looking to get a "Simple" DCC system
These are the questions I saw posed elsewhere and my answers:
How big is your layout? Still in planning stages, Either a 5'x9' or 1x14 shelf What scale? HO What will you be modeling? Freelance Who many trains will you operate simultaneously? 1 not more than 2 Will others be operating with you or will you be strictly solo? Solo Will you want to operate turnouts and signal with your throttle? No Will you want to incorporate a computer for programming? No
I have collected over the years a hodgepodge of models(a Bachmann Doodlebug, An F59 and Athearns Commuter cars, GP 38-2, FA 2, etc) and will be getting (in the budget) a small steam loco w sound.
Of the systems I've seen Bachmann's Easy DCC, Digitrax Zephyr, NCE, MRC Prodigy. Seem to fit the bill. Bachmann's system kind of worries me from the look of the construction but is the lowest cost. The others, bigger systems( maybe more than I need? ) with more capability.
I do not foresee needing a walkaround system just something that will run trains. I could probably just get by with a straight DC system but I would like to be able to put in sound decoders over time.(all the bells & whistles).
Not sure what to say
Many Thx IGN