I would definitely suggest Parelli. I don't think there is a better foundation to put on a horse personally. But I would caution you if you plan on mixing Parelli and more traditional training...the risk of confusing the horse is high and I personally don't believe in mixing differnt training ideas. But that's just me.
It's not about confusing the horse, but rather testing the waters and finding a mixture that works best for you. I prefer to use a variety of methods, and I firmly believe that the more you know, the better prepared you are to tackle different problems that arise during your riding career.
For example, if your horse has a problem with accepting the bit, perhaps one method won't work, so you try another, then another, and perhaps you need to mix a few methods to get your horse to find its niche.
Personally, I have to agree with LoveMyFinny... I have met very few "Parelli-trained" horses that have turned out well.
My biggest problem is that Parelli tries to teach things he knows nothing about... he gets his horse to "piaffe" and it's completely and totally not collection or impulsion-based, but rather just shuffling the feet.
I have a few issues with Parelli, I don't agree with many ideas of his... haha. Feel free to PM me if you'd like to chat more.