Perhaps he was using a 2 meter amplifier. If you're having trouble hitting a particular repeater improve your antenna first. Anything outdoors up in the air is a good place to start, but your needs may vary. Were you at home, in your car, or on foot? Are you sure your radio was set to use the maximum power?
I use a Diamond RH77CA antenna on my HT versus the one it came with. At home I use an outdoor antenna. On the vehicle I use a mobile antenna for 2m/440. What I don't use is an amplifier. If I did, I would first make sure the antenna could handle the additional wattage. Five watts is quite a bit to hit most repeaters. Know this, with five watts I can hit the S0-50 satellite and make a contact using the HT and the stock antenna that came with it. True there aren't many things in the way when it passes overhead, but it does work. Anyways, an amplifier will need a power source.
* There is a Diamond SRH77CA antenna that will work with the SMA connector on your HT. I personally use a BNC adapter on my HT, but whatever works for you.