Not that I'm an expert, but like everyone else, I have an opinion
For the last year or so I have manually dosed both of my tanks. The 15gal nano gets about 20mls Reef Advantage calcium solution and 15mls baked baking soda solution daily (for alk)and a 2gal (apx15-20%) water change every Sun....this tank has a candycane, pipeorgan coral and softies (zoos,GSP,mushrooms etc......)...so the coraline uses most of the calcium
....and this tank is very stable, the doses are small (read cheap) and the ionic balance is corrected every Sun with the water change.....ie small tank with low Ca demand...no reactors required.
But.....the story is different with my 90gal.....my fault, but illustrates the different needs of each tank. The tank has about 40 SPS, some LPS and softies...as well as a heavy coraline habit
.....making the calcium demand about 100 to 140ppm per week. Adding calcium and alk as in my nano and dripping kalk...I can't keep the calcium up and the alk fluxuates, as well as the counter ions (Na and Cl) dilute out the trace elements (esp MG) and can raise the SPGR. Of course this could be helped with a 20gal water change every week (ie $30 per month for salt)
plus $20 of calcium etc...
I should think that your tank (140gal softy) sits somewhere in between mine.
If it was mine, I would topup through a kalk reactor (cheapest reactor, regulate via stirring)), water change 10-20% every 1-2 weeks (and then test) calc. the alk, Ca and Mg needs and divide it into a daily dose (should be small).
If you are planning to eventually go with lots SPS or LPS then I would (and did) spend the money on a Calcium reactor (and CO2etc).....expensive but the best suppliment and stability....when set up right
Hope this helps....gooood Reeeefing