Hi sunjayraj,
Tai Chi Chuan (in Mandarin(PinYin), TaiJiQuan) is first and foremost a martial art, but in many ways and by many people considered a form of moving Qigong. In fact, Dr. Yang points out that any form of exercise that improves blood (and therefore Qi) circulation can be called Qigong, even walking.
You can certainly combine TaiJiQuan with any other form of QiGong as you see fit. In fact, if you are interested in trying the Eight Pieces of Brocade Qigong set (BaDuanJin) - it can serve as an excellent warm up for your TaiJiQuan practice, as it is a gentle and natural set of stretches for the entire body. Dr. Yang authored both a book and DVD on that set.
I have practiced numerous forms of Qigong with my TaiJiQuan practice for years, and found they have always complemented one another.
That is my experience, but I would urge you to try it and see what works for you. If you don't like a set, don't do it, find another. Everyone is an individual and will inevitably have varying results - listen to your body and mind and work out your own path. I used to want to follow a single author, so I could put things into a nice neat package. But, I've learned it is best to just develop your own way, in your own style, because what works for another may not work for you.
I have not read anything by Terry Dunn, but I find Dr. Yang's material to be excellent.
I will look into Terry's material as well, as I'm always willing to learn from another perspective.
Good luck, and above all enjoy yourself!