What's a reasonable budget for noticeably better-than-laptop sound?

Around $40 is the floor where reviewers stop apologizing — the Creative Pebble V3 sits in that band and gets credited as a clear upgrade over built-in laptop speakers. To get real low-end and accurate mids, the consensus jumps to the $120–$170 range (Edifier MR3, Klipsch ProMedia 2.1, Edifier M60).