As a fellow owner of the 325 I can say that the P25 auto setting does not always do the best job for decoding. You can try adjusting the P25 threshold to see if it makes the signal any better. In order to access this option you will first need to powerdown your scanner. Once it is turned off hold down the hold button while pressing the power button. When the orange light goes off and text appears on the screen you can let go. Once the scanner finishes booting up you can now press the menu button scroll to settings and you will find a new option labeled P25 threshold. Hopefully that will help you get better audio. Just so you are aware when you power off the scanner the threshold setting will revert back to auto. If you find adjusting the threshold setting works you will have to remember to power the scanner up each time using the instructions above and going back into the menu and changing the setting back to what you found works the best.
The W801 definitely works a lot better than the antenna Uniden supplies with the scanner. I monitor frequencies from 40 MHz – 900 MHz and the 801 does a good job. On a sidenote I know your question was originally about wideband antennas but when it comes to monitoring weaker 700/800 MHz this antenna is probably one of the best out there.
REMTRONIX 800 MHz Portable BNC Antenna | Scanner Master
This antenna was formerly known as the RadioShack 800 MHz antenna. With the recent downturn of RS Remtronix the original manufacturer of the Santana has started selling it more through vendors such a scanner master and universal radio. It has a very long history of happy customers including myself.