All RNS510 will work, but you will mosee than likely need a new CAN gateway, you are on the cusp of when the L came in (some K versions were ok but better to consider L as the minimum).
Battery drain in that respect does not happen with aftermarket HU's.
If you mean the DNX520VBT, I think they are not as good as alternatives these days (no cluster info display etc). The later DNX521DAB is much better.
I have had a Zenec NC2010 for a few years which 'out of the box' is better value and specced than an RNS510 and DNX520VBT, with full integration.