thinking about getting a catback for my integra that is a good price however its 2.25" instead of 2.5"

is this worth getting, or should i go for 2.5" (althought i wouldnt be able to get nearly as good of a deal)

how much performance loss would i get for going with the 2.25", i plan on eventually having around 190-200hp


also i was wondering if i have a b18b engine from a 95 integra in my 91 would i need different header than i would otherwise if i had kept the b18a


thanks