I'm using Spendor S8es which have a rear port and are only about 8" from the rear wall without any problems. (I had the smaller Spendor S5e prior to that and they had no issues either.) Spendor makes a point that their slotted linear flow port is designed to be less sensitive to placement near to a rear wall than some other designs. My experience supports that statement.
Of course, the best thing to do with ANY speaker is to try it in your listening room and see what you think of it before you buy.
Of course, the best thing to do with ANY speaker is to try it in your listening room and see what you think of it before you buy.