A little late to this thread, but I could help but wonder...
Is that rotting plywood you speak of due to moisture from your washing machine or other top-down sources, or is it likely due to the moisture seeping up from your concrete subfloor?
If the moisture is coming up from the concrete, you've got bigger issues on your hands. The moisture will continue to rot whatever you put on top of it, so you really must seal the concrete first, or find out if you've got a leak coming in from a wall somewhere.
Moisture from the top of the floor usually comes from:
a) Large spills of water
b) High moisture content in the air
With problem (b), a great solution could be a dehumidifier. Suck that moisture out of your air and keep the humidity around a constant 50/60% RH in order to stop mold and mildew.
If it's problem (a), it's really hard to find any click-lock flooring that will seal completely and not let moisture through ANY crack. You just have to be very proactive and fast in mopping up spills or floods. Even a little water sitting for too long can make bubbles happen in cheaper laminate floors or cause cupping in hardwoods or engineered woods.
No matter what you lay down, it's going to cost time and money. If you're interested in really the ONLY way to protect that investment...ie in the case of a large floor or really big spill, you really want a system that you can remove without damaging the flooring. That way, in the case of a big moisture problem, you get all the damage prone wood out of there, clean up the mess, and put it all back again.
Really the only think I've seen that can do that is a new solid hardwood system called Easiklip. It's a floating 3/4" hardwood that just sits on top of a standard underlay (i think). It uses a new clip system to attach boards to one another so nothing is ever nailed down. You can actually pop it up again once you've laid it. So in theory, if there's a big flood, you just pull up your flooring, dry up the mess and put it back down again.
Kinda cool and maybe worth checking out :) Here's a link to some installation instructions for the Easiklip system - take a look at the clips Easiklip Installation Instructions
Hope that helps!