There are a load of them going for around 150 on ebay right now, plenty of people trying to sell theirs. Check your local craigslist too, you might even find some there.
The fit is decent. It's a funky design but most people will definitely be able to get a good seal after a bit of tweaking and moving the earphones around. I've had mine reshelled and I feel like they fit significantly better afterwards plus the sound improved a lot, but mine had a faulty left nozzle so the improvement was probably a bit more than usual.
Headphone amp is absolutely unnecessary in my opinion. They get just as loud as my other headphones at a 10-15% lower volume I've found.
At $150 I feel that they are very hard to beat, provided you use the correct tips and get a good seal. They actually didn't wow me when I first tried them but after listening for a week or two they really grew on me. I'd definitely recommend them.