There's the phrase sehr wohl, which literally translates as "very well." But is this really a good phrase for a general approving "very well?" I've always imagined it being something a butler or servant says back to the lord upon hearing an order, Ja, sehr wohl, mein Herr. Your thoughts?
"Sehr wohl" in the affirmative sense ("Sehr wohl, mein Herr") isn't so much antiquated as it is subservient. I.e. it is only said by someone serving you, like a waiter or salesperson and sounds rather posh.
As such, it is rather old-fashioned since these master-servant relations aren't very modern anymore. You are more and more likely to be "geduzt" in shops or at least they try to create a friendly atmosphere and would respond to a request with "Gerne!" or similar.
The other use, as an amplifier of a statement, it completely usual in normal modern conversation.
It has at least two meanings. One is that you mentioned ("Sehr wohl, mein Herr"). The other is to emphasize something, especially if another person diagrees with one of your statements. Examples:
Was ich sage, ist sehr wohl richtig.
Der Klimawandel findet sehr wohl statt.