I'm also persuing a career in personal training. When I started college I had planned to do software engineering, then I swithced to nursing and was one semester short of becoming an RN before I decided I'd rather do personal training instead!
Now I'm majoring in exercise science, and honestly I'm mainly going after the degree as a formaility, just to improve how I can sell myself. Of course there area few classes that I'm excited about taking, because I'm hoping to expand my knowledge in certain areas, but mostly, it's just for the peice of paper.
As far as if a degree is absolutely necessary to become a personal trainer, then the answer is no. Honestly, most any dope with the minimum prerequisites can become a personal trainer if they're persistent enough, and this is very evident if you step back and evaluate the entire personal trainer community. I really wish there were more challenging requirements. But there are certain things that separate the good ones from the bad ones, and the successful from the not, and that's what I'm studying and researching so that when I start my career, I'll know what to do. Knowing your stuff about health and fitness is very, very important, but knowing your stuff about business and marketing is just as important.
A college degree will of course make you look better on paper. If trainer A and trainer B both have great personalities, know their stuff, and have the same level of experience, but trainer A has a fitness related degree and trainer B doesn't, then most of the time trainer A is going to get the client. I think when it comes to certs, as long as you have a good one that most gyms in your area will accept, then you'll be fine. Plus you want the respect of other trainers, so you don't want to persue a mail-order cert or something. When it comes to people though, the average person isn't going to be able to tell the difference in one PT cert from another, so as long as you have the ones you need, you should be fine. However, the average person is going to be able to relate to you having a college degree in a fitness related field, because it's a more traditional level of certification, versus a personal training cert that they probably know nothing about.
There are plenty of very successful personal trainers who do not have fitness related degree, or any college degree for that matter. I figured I"m in a good position just to go ahead and get mine, since I'm already in college, and since I need a couple more years to develop myself physically and mentally before I start my career. I'm the kind of person that will do anything to take myself one step ahead of my competition, and that's a good attitutde to have when it comes to business.
Strive for excelleance and don't let anyone stand in your way! Don't settle for average, like so many do!