Not at all. Its better to do things that actually matter and make you even a more competitive candiate (as in taking PhD micro); rather than finishing school in 4 years just for the sake of it. Adcoms are going to evaluate you based upon the given classes you took and the grades in them. I think Phd Micro and real analysis 2 should be the max you should take in one semester (unless you really believe in your ability to take more). PhD micro will eat up A LOT of your time and you cant afford to get even a B+ in it; for the grad students it doesnt matter.. they can just get a B and pass. But that is not the case for you as you will be applying to PhD programmes.