What mixes with Transparent Ultra Xl Speaker Cable

Excellent cable! Id run that to the panel to get the best out of it. For the woofer, You could use the Transparent Super or a run of Analysis Plus Oval 9. Very nice sounding cable.-Ken :)

I'd run it straight to the speaker and use the stock jumpers or get some transparent jumpers. You could possibly have the cable converted to bi-wire by Transparent?

Get the transparent jumpers which makes it equivelent to bi-wire cable (not bi-cable). Make sure to clean all connections as this will make a difference if you haven't done so before. Deoxit, or another cleaner.

Connect the Transparent to the top bindings spades, and then plug the banana jumpers(since you can't probably fit two spades under a binding post) into the top bindings and use the spades on the bottom binding post.

Do what Cytocycle suggests. Transparent's recommendation is that it's better to have a high-quality single cable with jumpers than use lesser cables for bi-wire. My previous experience has borne this out.

OTOH, if you can afford to go the Bi-Cable route at or above the level you're at now (i.e. Ultra w/XL or better), do it.

Transparent will reterminate to bi-wire. I had this done to my supers a couple of years ago - $225 if I remember right, and it took about a week.
I also have ML's - SL3's front, Aerius i's rear. Would use as a single cable with jumpers until you bi-wire.