I understand that during mining, one does not discover individual coins, but rather blocks of coins, and I heard that one block equals many coins (but how many?). I am wondering though, as a solo miner, what are the odds of discovering a new block? I guess this depends on my hardware but if we say that a GPU is 10 times faster than a CPU, and a $10 USB ASIC device is 1000 times faster than a CPU, and a $300 mining box is 5000 times faster than a CPU, perhaps one can adjust the odds estimations to reflect that.
Also, how many BTC would I obtain if I discovered a block? This website http://blockexplorer.com/ seems to how a variable number. But it seems a bit like winning a lottery.