You want something loud enough for a backyard, sturdy enough to survive spills, and built with a mic jack for karaoke night. A decent party speaker should last four to six years if you buy the right hardware upfront instead of burning through cheap plastic boxes every summer.
Audio brands refresh their lineups in late spring before warm weather hits. That means last year's models drop significantly in price during back-to-school sales and late fall clearances, giving you the same sound quality and battery life for around $300.
An intro zero-percent rate is a strict deadline, not free money. If you have any balance remaining after the 18 months are up, regular variable interest kicks in on what is left. Set up an autopay for $16.67 a month right when you buy it so the bill clears out quietly on schedule.