I would guess that in general, a PhD will not make up for a glaring deficiency, like a 180 step 1 score. However, it would help set you apart, especially if it comes up during your interview. I'm sure at the more research-oriented institutions, they'd probably view this favorably. At the med school I graduated from, there were hardly any anesthesia faculty doing research, and most of the residents did little to no research +/- the yearly poster at the regional anesthesia meeting, from what I could tell.