Unallocated is the most cost effective. Apart from that, you can never find a better place than buying face to face off the forum.
Aside from the forum I have found Ainslie 100oz bars are the most cost effective. Average 5-6% over spot.
I buy junk silver, normally at spot or slightly under. It just depends how much you like junk silver. A lot of money gets spent on postage so if you bu from a dealer see if they will store it for you so you can add several orders and only pay one delivery fee.
I've never seen an overseas seller that can beat local prices when exchange and postage is considered.
depends on what you are buying and your purpose APMEX may have items you cannot buy in Australia that would sell at a premium in Australia, ie arbitrage/flipping as a middle man might work if you are just out to make money off the price movement the please take note of the buy sell spread at present which is high. It is so high that it looks unattractive from the point of view of a investment. For example, looking at one example of buy and sell spread for the cheapest 1kg bar, 893.7 to buy and buyback is 815.97. The spread is 77.73, or 8.6%. This is the amount you need to make on that to break even, not counting tax, which will add to the burden of an already unattractive trade. The spread is so high that it makes spending the same amount of money on a silver ETF trade more attractive. For one - the cost is less by around 17 dollars, you don't have to worry about where to put it, you can sell at any time from your phone. What the poor current buyback price to dealers suggests to me is that there is a glut of silver in the investment market. When demand pickups up briskly, you'd think the buyback price would go up.