Tweeter Pop... Speaker Pop.. HU replaced

Hi guys, well this is going to prove my stupidity beyond a doubt! I have a 1999 TDI Beetle.. LOVE MY CAR. Head Unit (original) went out and had to replace. Wanted to keep stock so bought one off ebay. I got the monsoon version as I was not sure if my Beetle was or was not Monsoon.. this is my first VW. Stereo went in great and programmed easy. Now I hear tweeter pop at louder volumes and rattles in speakers. At lower volumes its not as noticeable but still there. SOunds like a rattle. The bass is horrible and I have to keep it very low setting or else the pop gets louder and louder. Any info on Monsoon vs Non Monsoon.. did I mess up buying the Monsoon HU. What about the speakers and tweeter pop... could the speakers have been busted by a different voltage? (Not sure if MOnsoon operates at different Ohm/Volt) Any advise would be appreciated. I dont want to replace the HU with an after market unit as Im proud that my car remains stock and is a deceptive little ass hauler. You would never expect a bug to be sucha bad ass!
Thanks
D

I don't have experience with monsoon units directly. But generally when speakers are popping then there is a problem with the amplifier or signal source. And pops can hurt the drivers if they over extend the voice coils and bang stuff in the driver.