Alpha-core advise?

I recently tried some Alpha-core MI 2 speaker cable and was quite impressed. When I made inquiries at Alpha-core, two different engineers gave me conflicting advise. Perhaps some one here can straighten me out. My curent system uses a Threshold S/500 series II driving Thiel 3.5's. The Threshold according to Jon Soderberg who used to work for Threshold is capable of doubling down. The Threshold is rated as 250 Watts per channel. The Thiels are rated as 4 Ohms nominal and 4 Ohms minimum. Independent tests show this to be rather accurate (an amazingly flat load) with one peak at about 33 Hz to about 8 Ohms. Ergo the amp may be pushing up to 500 Watts per channel. It was originally suggested by Alpha-core that I use a pair of MI 2's for my requested 8' run. They latter suggested that I run two pairs (not a traditional bi-wire situation). Unfortunately the speakers binding posts couldn't accept more than one set of the attached silver spades. When I called back, a different engineer suggested MI 3's. I'm a bit confused by the "characteristic impedance" issue. If one were to double up runs of these speaker cables, would the "characteristic impedance" half?, remain the same?, double? or something else? One advantage to this speaker cable line is that they can be made in such a way that they could have integral "spades" rather than added on ones. The advantage of the MI 3's over the MI 2's, due to greater width would be increased surface area if they were terminated in this fashion. The advantage of using double runs of MI 2's would be decreased cost and perhaps (and this depends on the answer to the previous question) better impedance matching. The Alpha-core web site suggests that this design needs little break in. Would these cables benefit from the use of a cable cooker? BTW, I am now considering using 3 meter to 10' runs. What's a boy to do?