My little bean is about 160 beats/min. I seriously think it's a girl, LOL!
Don't get your hopes up, my baby was 174 earlier on, and I thought for sure it was a girl. I was told he's a boy. The heartbeat will change throughout your pregnancy, most do, so don't get alarmed if it does.
As for the doppler, I rented one at 8 wks and was able to hear the heartbeat at 9 wks. I couldn't find it easily, it took some time, and I couldn't find it everytime. It was amazing to hear though.
Going a bit off topic, you know the sounds you hear on the doppler (swoosh-swoosh)? I received a bear at my baby shower that attaches to the crib and plays "the sounds of the womb." Its supposed to calm baby in the beginning because it brings them familiar surroundings. I'm bringing this to the hospital with me since I'll be there for 3 or 4 days.