I hate RO, too much of a bitch, too expensive, and does too good a job, so now you have to add the good stuff you just filtered out, err RO is overkill 90% of the time. If you own your home you will want to get that down for the whole house anyway, unless you like plugged up and leaking pipes or paying to fix them.
I rent so there is no water softener or any chance of a good whole house filter situation.. Yea, I'd like to see how well the aquasana filters perform.. Now that I checked my TDS I am scared to make coffee with the tap water
I think so. If you mix it 50/50 with RO water you'd have a better starting PPM. If you're in the US, federal law requires your water provider to publish an annual water quality report. They can usually be found on the provider's web site. I'd examine that to make sure the minerals are reasonably balanced, suitable for growing (if reduced to a lower level with RO water).