Your worrying to much, don't believe everything you read in those reviews.
The grills are fine, they snap in and stay in place. Occasionaly someone will have a defective fastener and Axiom replaces them no questions asked.
The VP150 is a great center, again many like to give it a bad name, not sure why. Centers are primarily used for center dialog in movies and voice in some audio tracks. Again, not to worry.
The Axiom centers and surrounds go plenty low for their intended use. Start with 80hz, as that is the norm and follows THX guidelines.
