If you must mount it on the coffee table, I would try to get a coffee table with a lower shelf and mount it in that, then route the cables underneath the coffee table, under your couch, then along the baseboards. I hate seeing wires, and I like tripping on them even less. That said, you will see a phenomenal improvement in comparison. You are getting:
1280x720 = 921 600 pixels vs 1920x1080 = 2 073 600 pixels in the same screen size. What this means is a much clearer image (that, and you can sit closer before you begin to see pixelation, so it's more immersive). You may not like 3D, but the processing power needed to run the 3D also means a much cleaner 2D image. It is leaps and bounds above my old BenQ W5000 (a 1080p unit). It is the cleanest image I've ever seen. Amazingly, the 3D image is even more clean/clear than the 2D one. I'm not sure about black levels, but your H78 is a Dark Chip 3 and may trump the HD3300. The blacks are plenty fine for me, though.
About brightness, it is definitely plenty bright. Especially if you plan on having it in a coffee table in front of you. Good luck!