Save your money if all you want is a more sensitive radio. Every transceiver on the market can hear well below the natural noise floor of anywhere on planet earth. -120dBm is as low as it gets and even CBs can manage below that. Where they do vary is in selectivity, the ability to hear a weak signal next to a strong one. If that isn't the issue you would be better off putting the money into your antennas first and the radio second. Better antennas will bring in those currently weak signals better. A new transceiver won't.