firstly, no you cant have both, one is a replacement filter to go in your existing air box, the other replaces the airbox entirely. second question, it depends on the car and how much you have to spend, if you havent got a valver/williams/172/182 i would say go panel filter, an ITG will give you better thrttle response but no real gain in power. If you have one of the cars listed above then an induction is worth considering, though i have not heard of one thats makes huge gains on the valver or williams so would again recomend an ITG panel filter. though for a 172 or 182 i would say either BMC CDA or ITG Maxogen. any more questions feel free to pm me.