#3 -- I think that's why I favor silver over gold for the larger bars. You can easily do a test with a rare earth magnet and mix in the "ping" test for proper sound. With gold, you need to be extra extra careful and fire up that ultrasound machine.
Sorry for being slightly off topic, I don't know quite as much about testing gold, so I would probably make sure you buy from a reputable dealer. If you are going to acid test small 1oz bullion, be sure you aren't getting anything for its collector value, as you need to cut into the coin to properly acid test it, and it will completely ruin any collector value.
Also, I can understand your desire for a 1 kilo bar. I think there's some innate "ecstasy of gold" mentality built into all of us. The truth is though, its definitely not the smartest buy. 1 Kilo bars are purchased by BIG time investors, and not by the single bar-by the hundreds, maybe thousands. Since you (Teran) are such a nice guy, I want to do what I can to steer you in the right direction. So I'm sorry if I reiterate at all. But here are my compelling arguments:
1. The only reason for buying any precious in a larger increment is because you pay [negligible if you only buy one] less of a premium over spot. For example: it costs A LOT more to buy 10 x 1/10 gold coins than it does to buy 1 x 1oz. SO, buying 1oz bars may cost you a bit more over spot than a kilo bar would, but you get that money back in the form of the same premium over spot that you paid when you sell them. ALSO, more compelling, selling a 1 Kilo bar is A LOT harder than selling 1 oz bars. With 1 oz bars you can have as many paydays as you have bars. With a kilo bar, you get one payday. Also, if you got one ounce bars they would most likely be PAMP or Credit Suisse, which are universally recognized and thus easy to trade. A kilo bar would most definitely have to be assayed.
2. Refineries usually make 1kilo bars with the buyer in mind-they know they're not going to be looking at, appreciating their gold. One kilo bars are often-for lack of a better term-ugly. Also, you questioning if a kilo bar would be worth more doesn't hold any water. Any refinery can take 1oz bars and turn them into a kilo bar.
3. Finally, there is the argument of authenticity. If you buy 1oz PAMP bars from a reputable seller, you really don't have anything to worry about. Kilo bars, however, are sold by less vendors. Often they are even marked with a sharpie (told you they were ugly)! It is very easy to load a 1 kilo bar with something like Tungsten. And it would be relatively hard to detect. Think of the Tungesten in the I believe 10oz bars sold by a reputable dealer. If it happened with 10oz bars, it would/could certainly happen even easier with a 1 kilo bar.
Finally, the choice is yours (obviously). I know that having a kilo bar and playing with it would be fun. But bathing in a bunch of 1oz bars isn't so bad either!
I wish you the best in your buying decision!