Safari Suggestions

Hello all. I'm going to be heading to Kenya for some field work, and at the end of the week some of us were thinking of tacking on a 2 or 3 day safari excursion to Masai Mara Park. However, there are literally hundreds out there, and so trying to sort through them has been a Herculean task. I was wondering if anyone had suggestions as to outfitters that are good, reliable, and reasonably priced (don't have an exact figure for that, since none of us have gone before). Any help is appreciated. Thanks!!