From what I gathered, for US silver coins, (not "junk') the going rate seemd to be about a buck and a half over spot.
(Note: lots of personal opinion follows, so please read it as just that... opinion)
Do you mean specifically coins minted by the Goverment ("coins") or just any silver "rounds" minted here? If you do mean coins, the only non-junk coins I can think of are the US Silver Eagles and numismatic silver. Personally, I do not consider numismatic coins for two reasons. First, the premium over silver content depends on other people also valuing them for scarcity and suggests strongly to me the "greater fool" investment theory. Now, some people really do seem to enjoy collecting numismatics, and that's great. But that is for personal enjoyment. I would not recommend them as an investment. The Silver Eagles do indeed seem to carry a hefty premium, as you say, a buck and a half from both CNI and Tulving. They are indeed nice looking, but personally I would not buy more than a modest number for personal "enjoyment" and for giving as gifts.
Every penny needlessly spent on premiums over the silver content is a penny that can not be used to buy silver

Now if you are loosely using the word "coins" to also include silver rounds, then we can get more silver for our FRNs

Unfortunately, fifty cents seems to be the common premium over spot, but as spot price edges toward ten bucks an ounce, the hit doesn't seem quite as bad as it used to. I have often noticed that both CNI and Tulving list their spot closing price a few cents higher than what I though the real closing price was. I could be mistaken, of course, and I would recommend either one of them; just keep your eyes open

Since the spread seems to almost always be buy at spot and sell at plus fifty cents, I mentally figure that I could get 25 or 30 cents over spot in a private person to person deal.
I have not done business with APMEX, but I have read many good reports about them. Just be aware of the shipping charges. Right now, they have some 10oz bars at ten cents over spot

I would prefer those over the 1/2 to 3 ounce sterling bars and rounds. In this case, I would spend a few extra cents to get my metal in a known size and purity that everyone understands.
Used by folks as a medium of exchange, IMHO would be a vehicle create some revenue for FSW.
I am not in favor of the practice of seniorage, that is, taking a large profit from the minting of a trade money. If someone else wants to do it and others are willing to pay the premium, that's fine with me. For instance, I have nothing particularly good to say about that guy selling "Liberty Dollars" where he sells an ounce of silver for $20. Huh?! The way I see it, I could buy almost twice the silver just by buying generic rounds. And (in my opinion, as always!) his paper notes are just not the same as holding real silver. This guy might be the most honest fellow in the world, but if something happens and I cannot go to his vault to redeem his notes for silver, they might as well be FRNs.
My motto is, "If you do not have the PHYSICAL metal, you do NOT have it." Obviously, one does not need to keep the metal in the house, just that it must not be under someone else's control.