Too many variables for us to say for sure, mikie. Writing bass parts, recording bass lines, even playing along to a loud stereo at "near garage band volume" a 200 is plenty. But, when you get other guys
jamming, and possibly playing large venue gigs, then all bets are off. It
might, conceivably, be enough but chances are high that it might not be! It's your chance to take, if you're a ramblin' gamblin' man.
But, if you wanna hedge your bet, and future-proof your purchase, the 500 is the surest way to go. It'll definitely handle very loud bands. Of course, there's also a chance that Murphy's Law then dictates that you'll never turn the 500 up past
9-10 o'clock (curse that 'Dog for selling me more than I needed!).
.