How much should I spend on a 6.5" speaker upgrade?

Across the reviewers we read, $60–$130 a pair covers the sweet spot for stock-head-unit replacements (Rockford Fosgate R165X3, Kicker DSC650, JBL GTO609C). Above $200 you're paying for true high-resolution component sets like the Pioneer Z-Series, and that money is wasted unless you're also adding an amp and doing some sound deadening.