Naaaah...what you need, if you're getting an external scope, is one that can ALSO be used in an X-Y mode. If you're doing a lot of bassheavy stuff, keeping an eye on low end phasing is a MUST, and a dual-tracer in X-Y can give you phasescope results when you connect the two stereo channels to the two inputs on the scope. Why? Well, if you're tracking for vinyl, you'll find that bass signals below somewhere around 120-180 Hz can cause SERIOUS problems for the lathe engineer. So as a rule, bass below that certain point can cause havoc if it's out of phase, so it gets summed down to mono for vinyl. Keeping an eye on phasing while mixing, also, helps you get to better mixes with some practice, especially when doing a lot of panning and other screwy imaging processes.
FYI, eBay has a pile of suitable o-scopes for $200 and down...just make sure that you get one that's dual-trace with X-Y capabilities.