Susan.. Hello from Findlay Ohio. I hope you are staying warm in this frigid weather. The touring operators that you listed are all (If Tropical is Tropical Trails) located in Tanzania and are Tanzanian companies. I know some of them personally and they are reputable companies. I hesitate to offer recommendations because it is difficult to know what you are expecting from a safari, and everyone has different expectations. Most any reputable local safari company will know the territory and can put a good safari together for you, the driver/guide who takes you out is the person who will make the safari enjoyable and worthwhile, thus it becomes much more then just the company which makes the trip a safari to remember.
Having said all that, most reliable companies always make certain that their driver/guides have the proper experiences, speak excellent English, have been properly trained, treat their clients nicely, and understand safety rules.
I understand that you can quickly become overwhelmed with information, but pick out several of the operators that you feel comfortable with, communicate with them, find some people from the US who can provide references and call these people and talk with them about their experiences with this company. From this you'll begin to get an impression of the companies that you'll be dealing with.
Probably the most important thing that you could be doing is to make certain that the safari company knows and understands what your expectations are (specifically with no assumptions) so that they can put something together for you based upon these expectations. I've seen many people come there with unstated expectations and then be disappointed when these weren't met, but they could have been if they would only have told someone. Another mistake some make is to try to micromanage their safari down to every lodge to stay at, then be disappointed and think their safari is ruined when there is no availability at some lodge. Allow serendipity to provide you with some surprises.
Get your bookings in as early as possible as lodges do fill up quickly; some are full now for certain times. No lodges will be reserved for you until you pay your deposit.
Fortunately, most of the safari companies which are local are good companies and they want you to have a good safari.