I finally got it removed without further assistance.
My bad:
In addition to the 3 circular "push-pins" AND the 10 mm nuts I found there was also some super-sticky double faced tape holding the piece to the trunk.
Firm, slow pressure prying with plastic body tool eventually got it free.
The tape was SO tacky, that it felt like there was some other fastener I had missed.

 

I took the chrome piece off then realized I should have just routed by the license plate light covers, but I used a license plate frame type. Here's my thread: http://www.toyotanation.com/forum/1...d-generation-2000-2004/1066546-just-picked-up-2003-xls-white-2.html#post9964810

 

I took the chrome piece off then realized I should have just routed by the license plate light covers, but I used a license plate frame type. Here's my thread: Just picked up a 2003 XLS, white.

Can you please post a pic of what you wish you had done? I can’t really visualize it. I kinda don’t want to have to remove that chrome trim.

 

I sorta did the same thing. I ran out and got rubber grommets that would barely fit over the RCA plugs and THEN realized they wouldn't fit over the square box that's about a 1/2" square about 24" up the cable.... another DUH moment.

I did a slight mod from your method.
I elected to remove the license plate light-box and dremel-tooled a small notch in the side of the plastic case. That way. I figured the plastic wouldn't need to prime-painted like a metal cut would to prevent rust. I'm guessing that since the heat from the license-plate lamp doesn't melt the basic styrene lamp housing, it shouldn't melt a plastic cable routed around the far corner. The light-housing and the cable are two totally different types of plastic, but I can't imagine that the side of the lamp housing will get hot enough to be a problem.
I'll attach a pic if it works out. Obviously, I haven't reinstalled the chrome "garnish" piece yet. (I found out that is what Toyota actually calls the chrome piece.)

 

Well done. It's the easiest way to get that block through there.