Matt,
Have you seen those small display ads in papers like the Sunday New York Times, Travel Section which offer cheap fares to many destinations. Many are for very specific areas like India, and only use Airlines which are native to those areas.
Many of these ads are from 'Travel Consolidators' Who buy up blocks of tickets for future flights and sell them cheaply.
I have used them in the past (but I haven't been to Europe in recent years) and have been satisfied. I have recommended them to many people, but most are afraid to gambel, as they don't issue tickets. They give you a chit which you turn in at the airport for your ticket just before the flight.
I used a New York City travel agent at the time because New York Travel Agents must be 'bonded' by law, and I was more confident that my agent would not vanish in the night.
I was even able to arrange an Open Jaw trip. On my last return we started home from Rome, with a very short stop in Nice, to pick up more passengers and then on to New Your. The person who sat next to us in Nice paid more for his Nice-to-New York than we paid for our Open Jaw Round Trip.
Even it you don't want to us them, they give you a good starting point for looking for a fare price.
Leo