If he didn't test for and find tannins, he is just wanting to sell more equipment and raise the price. I really don't like guys like that. And the only thing Kinetico is the control valve, usually the rest is the same stuff I and other independent dealers sell. So ask him why such a high price. Far too many Kinetico dealers and their salesmen are like that; IMO they're crooks.
Is the sulfur odor in both the hot and cold or hot or cold only? Have you had a Coliform bacteria test done? If not get one done.
And why don't you want to install your equipment yourself, you may not know it but you may not have to solder? And it only takes about two hours and will save you hundreds of dollars; and, ya git braggin' rights! Plus, ya likely will become a handyman hero to she who you love and must obey, whether she admits it or not...There's certain side benefits to that. Especially if you buy a new smelling leather tool belt for a pair of Channel Lock type pliers, an adjustable wrench and a tubing cutter.