If you are sure you will be going to lithium in the future buy the 30A DC-DC. I like the ability to program the Victron to whatever you want. I have 2 Victron DC-DC 30A chargers. Two 270Ah BB batteries. #2 AWG feeding the chargers 150 amp circuit breaker on this line. I split the 2 AWG to 4 AWG with a dual 60 amp fuse block. They do get hot, I mounted vertically and spaced off the chargers off the wall with aluminum flat bar for more air flow.