itg maxogens?

ok, ive been looking at all the CAI's for a while now and ive come to the conclusion that all the good ones on the market (ABD, Carbonio, K&N typhoon, injen cai, etc) are all too expensive. so im thinking of buying the ebay kit just for the pipe and then get a filter seperately and just swap them over.

so, which is the best size filter to get cos they are all the same style just differant sizes.

should i just go for the biggest one or do i need a specific size to get the most out of it?

thanks in advance, dan