Since you are in Australia, you should probably look for or host games with AUS in title. A good name is ex. "AUS 3v3/4v4 Free kittens!" or something to that effect. You will naturally have a harder time finding a game than your US/EU counterparts, but I see AUS games around. You can also play on US servers, but expect to be ping kicked by people who was apparently unaware pings go over two digits.
256kbit is the minimum upload for 5v5, so it looks like you are right on the edge. But 5v5 AUS games are fairly rare in any case. Bandwidth requirements scale down with less players naturally, so try to see which games your ping remains stable at. If it fluctuates greatly, it's a good sign that your band is too narrow.
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