When it comes to the cheaper China HT's you get what you pay for. They will for sure get you on the air, but they will not perform as well as a radio from Kenwood, Yaesu, Icom, or Alinco.
I also agree on not using a magnetic mount if at all possible. Mag Mounts are supposed to be temporary antennas and do not provide near as good of a ground as a permanent mount does. A permanently installed and drilled NMO mount will perform much better than a mag mount antenna.
I'll second the Larsen NMO 2/70 for mobile use. I use one and it's a great antenna, Larsen is probably one of the best mobile antenna manufacturers for VHF/UHF. There are also several good base antennas that can be used at home that will work much better than the rubber duck antenna or a mag mount. The key is height, the higher up the better. In the car, I have my NMO mount on the center of my car's roof and it works much better than down low on the trunk of the car.
So, here's another vote on finding a good mobile radio to supplement your handheld.