Yes, yes, and no.
The HP head basically turns it into an XT HP. HP models just feature new head/reflectors. The run time and total overall light output, or Lumens will remain the same. The light fill have better ability to focus into a tight, far reaching beam, and have a higher intensity spot, or candlepower. The HP claims 40,000, over the standard Stinger 15,000. The light won't be brighter, just more focused to where you will THINK it is brighter.