My Phonak PFEs are falling apart - both wires have already cracked near the drivers, and they're hanging on with some electrical tape I've wrapped them with. I'm sure they'll end up snapping before long, so I need to get a replacement.
 
I've been quite happy with the PFEs (outside of the build quality!), and I have enjoyed their accuracy and detail compared to all prior headphones I have owned. However, I was never really satisfied with their low-end performance. I had to switch filters and use the bass boost on my amp and EQ just to get what seemed to be a balanced sound, and by doing that I am fairly certain it sacrificed accuracy and SQ in the process.
 
Does anyone have any recommendations for IEMs that have a great soundstage, an excellent low end, as well as good isolation and comfort? I'm hoping to spend less than $150 .. significantly less if possible.

You could try finding a triple fi around that price on eBay. I could imagine there being a lot of them for sale due to the recent amazon sale. Other than that, i'd recommend the Monster Turbines.

How old is your PFE? It has a two years warranty FYI. Also, the first batch is known for build quality problem and Phonak has promised to replace them. If your PFE is the old batch. you should contact them directly.