"......does it make any sense to ALSO have a dedicated filtered cold water tap at my bar/coffee station sink?"

If your tap water tastes like mine, it certainly does!

Believe you're talking about two issues 1) scale/deposition and 2) taste.

Scale/deposition can be handled via water softening. Taste can be handled via filtering -- typically via activated charcoal stack. Taste is a very individual thing. How far you should go is up to you.

In my case, local city water is 7-10 grains hard; about 200ppm TDS; and tastes distinctly alkaline, which is a region-wide characteristic. It leaves scale on heating elements and bad tastes in coffee, tea, rice, pasta,.... just about everything. I have a softener delivering zero grains to everything. Also have RO unit with sink spigot delivering water at 2ppm TDS which is also piped to the ref. ice-maker. Anything consumable in my household that is prepared using water gets it from the RO spigot. Many people do not like the taste of soft water or RO water and have their personal favorites among the bottled waters.

In any event, you should start out by knowing what's in your water now. Have you had it tested? Interestingly, although you talked about filtration and all your various concerns, you said nothing at all about whether or not your water tastes good/bad/neutral. Nor did you say whether or not you've had trouble with it previously.

As a devotee of the bean and a stone caffeine addict I'm here to tell you that high end espresso and coffee hardware loves RO water. My Krups, Opod, Keurig, and old school espresso have all been running every day for 8+ years without a single de-calcification or a second out of service... God forbid. Filters won't do that, but ROs do.

I also run RO water to the ice maker in the fridge... love those clear ice cubes... iced coffee!

Thx for the responses. Taste of water is just ok, but thought the drinking water would be fine from the filtered fridge dispenser. I am mostly concerned about my espresso machine. I have been using bottled RO for the machine to date, but my new kitchen doesn't have room for the water cooler and I hate going to the store to get refills. I was really hoping there is a filter system, RO or otherwise, that will do enough to prevent scale buildup in my machine. As I said above, I really want to avoid a second spout and was hoping to get something that fits on the main faucet. I know that's unlikely with RO, but I thought maybe a system like the EWS 2 stage voter that was recommended on the kitchen forum. I am researching current water quality but haven't determined it yet. I live in a suburb of Toronto, and I know it isn't too bad but I don't have specifics yet.

If the longevity of your espresso machine is your concern and you've been happy with RO water in it then you have your answer... and a possible solution is a countertop RO... click here