Thanks for the suggestions. I realized last night that a soffit is pretty much out of the question, as it would have to run right where a motion sensor (existing security system that I haven't yet activated) is installed... The other side of the room does not lend itself well to a soffit (back of the fireplace, wood enclosures for the furnace and water heater, and a recessed door to the living room in between the two;
Here's a rough mockup of the room I did before actually moving in; the back corner shelf is gone now)...
Given that, I'm thinking there are two places that will best lend themselves to rope lighting:
1) on the back edge of the screen for indirect ambient light
2) on the front lip of the back seating riser that I plan to build eventually...
#1 would be good to have controllable (I looked at the X-10 site; are those products also sold at stores such as Home Depot and Lowe's?) to adjust the lighting to the movie or turn it off altogether, but I would think #2 would be fine once dimmed to the proper level. I plan to plug the rope light(s) into a power strip used for my amps and subs to turn them on all together, so that would be a convenient way to turn the lights on at the same time.
I picked up the two 18' sections for $7 each at a discount store (just browsing through after visiting the lumber yard next door), which is a few bucks less than I've seen them anywhere else. Unfortunately, 18' isn't quite right for any one dimension I'm working with... For my intended screen size, it needs to be more like 22' to wrap around the perimeter, although I don't see any reason why I couldn't make a smaller inner rectangle to wrap the 18 footer completely around and just dim it less.
Dan