That’s a wise decision 
A second 555PS makes a tremendous difference.
And if you enjoy classical music the difference is simply astonishing!
There is no going back. It is that simple.
We really get used to sound, especially when it sounds “right”. It was only when I disconnected the second 555PS that I realized how good the ND555 + 2xPS was.
So yes Tim, a twin powered ND555 heading a 500DR amplification driving your Titans 808 will undoubtedly be an outstanding system!
If you didn’t enjoy symphonic music in the past, you’ll enjoy it now.
For that kind of demanding music, speakers like yours and a good source are both necessary, unfortunately.