1. Port noise is basically air rushing through the port too fast. The way to overcome this is by increasing the 'surface area' of the port i.e. using a larger diameter port. The problem with using round ports is usually you need a pretty big 'pipe' to get your port mach,speed of the air, to an acceptable level. So the way to get around this is to use multiple round ports or a slot port. A slot port uses one wall of the box along with the top and bottom with an additional wall contructed inside the box. This allow you more square inches of surface are than round ports.

examples of slot ported boxes:

http://community-2.webtv.net/MarvsPl...ace/page2.html

2. There's advantages to doing both common and seperate chambers. For instance with a common chamber box your port will not have to be as long. However, if one of the speakers were to fail then the other would probably fail because the enclosure is so 'uncontrolled'. This wouldn't happen in a seperate chamber box but the your port length will be much longer. Another thing to consider with a 5 cu ft common chamber box is you'll have to brace the crap out of it.

As for the size port you need: those two subs tuned to 32hz require 43.47 sq in minimum. A 4" round port is about 12.3 sq in. So you would need 4 4" ports to get adequate surface area each of them would have to be 23.5" long. Or you could do a single slot port 15"x3" 16.7" long.