The 500 gives an amazing grip and openness with the Active Ovator S600 - I ran mine non-DR for many years after upgrading from 300.
The 500 has the better open-mid clarity and bass speed and texture I found.
Then you have the 500 and can later get them up-lifted to DR when funds permit.
Yes 500’s x 2 i feel is the way to go as long as I keep my speaker’s, but i would like to try some atc scm40a on my system as that also looks like it could be good and much cheaper