ELAC isn't know for blow-the-walls-down Sensitivity. By most accounts they aren't bad Speakers, but 85dB Sensitivity and "140w" rating, there is only so much you can get from them. Honetly, I seem to recall several years ago, the ELACs were regarded as being a bit too "polite" if anything.
The Outlaw Amp is also very well regarded as a good quality Amp, as are the Monolith offerings. 70w more juice from the Monoliths won't really equate to much more than about 1dB increase in SPL.
You aren't in a very large room, and I can't imagine that you are sitting much further than about 8' from the mains unless you are backed up on a wall. Given that, 128w is enough to hit Reference level peaks (105dB) at 1m, maybe a little less at seated distance, but it should still drive you from the room unless you are already hearing impaired.
I think you bring up a valid question though in how your system is setup. You would need to show us some photos or a diagram of where your seated position and speakers are to better understand how your setup is... or just compare against the Dolby setup guides. Sometimes Speaker placement can be the biggest probelm, especially fitting a 7-channel bed layer in a small room.
Likewise, how Audyssey calibrates your system can have an impact...
...So, many other variables that can be at play affecting your system, not just the Amp.
If you are unhappy with the Outlaw and want to return it, go for it... just don't fall victim to the idea that an Amp will fix everything. You may find on honest reflection that the Monolith isn't much different... or you'll be completely blown away that some veil was lifted.
