Double your displacement with four more cylinders. That should give you something close to the sound you're looking for.
An I4 will never sound like a V8. It's a different beast entirely.
That being said, the exaust system will have a large effect on the sound. Here's a recent thread with some discussions on Prelude exhaust systems:
http://www.automotiveforums.com/vbulletin/t25146.html
