First of all, there's very seldom any such thing as "sulfur in the water." What causes it is bacteria, which generate hydrogen sulfide gas. That's what you smell. When you "bleach" the well, it kills the bacteria. For a while. Run a glass of your stinky water and let it sit for 20 minutes. Then smell of it. Still stink? If not, there's no sulfur. It's the hydrogen sulfide gas that escaped from the water. If it's really "sulfur in the water," it would stink an hour later.
Be REAL careful about these water filter sales people selling you all kinds of junk. Our well water stank, too, until I looked closer. Check: does it smell like that AT THE WELL, or just coming out of the faucets? If you run just a cold water faucet for a while, does it still stink, or is it just the hot water - again, after running for a minute or two.
If they know what they're doing, they should be able to talk to you about hydrogen sulfide gas. Just ask them, "how do you know whether it's really sulfur, or hydrogen sulfide gas?" If they give you that deer-in-the-headlights stare, politely say good-bye, and call somebody else.
I must have had 4 or 5 different companies try to sell me injection systems, evaporation tanks, etc. for THOUSANDS of dollars, and it was all snake oil. What causes the stink in many cases is the magnesium anode in your water heater. It interacts with the water chemistry and creates - you guessed it - hydrogen sulfide gas. Replace it with an aluminum or zinc rod and within a few days the smell will vanish. It's dismaying how many people don't know about this. The water filter industry makes tons of money off of them.