I'd leave the porting in there. Put in a couple of 8 ohm speakers in parallel and you will have 4 ohms, typical load for many amps.
If you have a closed back speaker cabinet you need porting. Putting tweeters in there will not provide any porting (air).
I have a rack system with a Peavey Transtube Fex and a MosValve 500 power amp into two separate 12" 1203-8 Black Widow speakers. It's a great outfit. I don't know what they would sound like if both were in the same enclosure.[This message was edited by Jack Stoner on 16 January 2001 at 03:32 AM.]