I’m also using an e2180. I have it currently at 3.0GHz, using a 3:2 FSB: DRAM ratio. My DDR2-800 memory runs at 900MHz when using that particular divider. If your using cheap memory that cannot accept a good oc on the ram, then using a 2:1 divider will underclock the memory and hence give it a large headroom to oc the cpu.
Power consumption does increase when oc’ing but not by the amount that you have read, its much less. Also most people that are oc’ed don’t run their computer at 100 percent all the time. Your can test the difference in power consumption with a ‘kill-a-watt’ power meter.
Your MB is very OC’able and so is your CPU, but it depends on a lot of things, like how cool your case runs, whether or not your using the stock CPU cooler, the quality of your RAM.
Increasing the cpu voltage is done gradually to make the cpu stable when oc’ing. More heat is generally created when doing so becuase there is a certain ‘leakage’ current that gets greater with increasing voltage. With the stock intel cooler you should probably be able to reach 2.8GHz.
Overclocking is a balancing act, and there are some tests that can be done prior to starting. The first is to find the maximum FSB the cpu is capable of. This is done by decreasing the cpu multipliler to the minimum, 6x for the e2180, and underclocking the memory with the 2:1 divider. Then increasing the cpu speed and testing its stability in windows with a program like Prime 95, or Orthos. Those two programs are capable of fully stressing the cpu cores to see if they are stable. After finding the max FSB, you then have an idea of how fast the cpu can go, but this is not factoring in the heat generation that will occur when rasing the cpu multiplier back up to 10x.
The next step is to find a safe speed and voltage for the RAM without stressing it to hard to insure long life. For example I decided to run my ram at ddr-900 with just 2.05V applied, the ram is capable of much higher 2.2V and much higher speeds.
There are some good basic guides to oc’ing a core 2 duo processor, that should give you more insight on the web