We know nothing about them despite having been pretty active on various travel boards and having visited Kusadasi on 4 ocassions (most recently this past April). Probably the oldest best known (and highly respected) tour company is EKOL. They are reliable and use excellent guides. However, the one negative is that that insist on a deposit (we actually pre-paid our most recent tour with them and got a 25% discount). The other company, who is the new player in game, is called Hello Ephesus. Although this company is new, it has been getting rave reviews from cruisers for the past few months. Hello Ephesus does not require a deposit which is a real plus. We do strongly recommend doing a private tour and avoiding the cruise line tours to the ruins because the cruise line tours do not generally include the Terrace Houses. The Terrace Houses are not to be missed and are simply amazing.