If you're going to get into this hobby, I think an RO or RO/DI unit is invaluable.
They really aren't too expensive and as mentioned, when factoring in time, gasoline, and hassle, are well worth it.
They are very uncomplicated, both to set up and run. I got a 5-stage from Air-Water-Ice and it took less than an hour to set up and get running . . . and that time included a trip to a big-box homestore to get a few doo-dads because I ordered the wrong source connection.
Filled our 90g the other day and can't for the life of me imagine what that would have taken if we had to go fetch that amount of water from source other than the big bucket in our laundry room.