Indeed I'm not a basshead, but perhaps we have different ways of defining bass. I can appreciate strong bass, but it must be speedy as well, and unfortunately the IM70 didn't quite feel fast. While I may exact fairly high standards for bass speed (think EX1000, 1Plus2 style bass), it's achievable in this price range, like with the JVC FXD80. That is a bassy earphone but with tight, fast, textured bass that hits hard and then harder. Maybe "would not recommend" is a bit strong, but I would hesitate at calling it a bargain.
We disagree on speed and bargain here, but I've agreed with you on your assessment of other products. It's all good. There was something that didn't totally gel with me when I first heard the IM70, but I heard the potential. It all came together after burn-in. So I'm wondering did you burn it in good (or do you not believe in burn in)? I can't remember if you're for or against the burn-in concept. Also, the IM70 changes a lot in the bass region base on tips. I think the Phonak tones the bass a bit that would be more to your liking (but still more than the IM50 based on your impressions). Nevertheless, I will agree that if the IM50 is that close to sound to the IM70 (sans less bass), it truly sounds like a great bargain too. I would fear it wouldn't have enough bass for me though. The IM70 just hits my basshead just right. I wouldn't want anymore bass unless I was seeking an all out basshead headphone, and I'm far from desiring that right now.