Hi guys, so far i've been producing and mixing everything on my Audio Technica ATH-M50x headphones for the last couple years. I'm trying to decide if I should invest in studio Monitors or maybe a new pair of headphones for mixing purposes. I can't go too expensive and I was set on going with the JBL 305's but now I'm not sure if getting some decent mixing headphones would be better. Would the AKG 701's, Beyerdynamic DT 880, or Sennheiser HD 650 be that much of an Upgrade to my Audio Technica's (which are closed back)? Or is it time for studio Monitors although I really can't buy anything more expensive than the JBL 305s?