<p>Grad schools would rather see more research experience than more math classes. Though being a math major does mean you have no excuse for not acing the quant section of the GRE (not that any of the stuff you cover in upper level math classes is on it, but it keeps you in a math mindset). </p>
<p>In general, they probably do not care one way or another what else you’ve been studying in addition to your major. You’re in grad school to dedicate all of your time and effort to your intended field, and if you’ve been doing that already, that’s just fine by them.</p>
<p>It might help slightly with a grad school but honestly I don’t think it would help all that much. AND, I think it may be wise to steer clear of the mindset that you need a PhD to have a high paying, stable career. My point is that you do not need 4 years of highly specialized knowledge for most industry positions - in fact, in many cases your knowledge with a PhD is only going to be of use to an extremely small number of firms that just so happen to have some dept related to your one miniscule area of research… Now, don’t get me wrong - there are PhDs in industry - but these are the exception, not the norm. Get a PhD if you are interested in the research, in academia - but don’t do it for industry, it’s simply not needed 99% of the time.</p>