Focusing on Watts like that is the wrong way of looking at it, as that "power range" is misleading, and that 300w max is either maximum sustained or a failure point... either way it is LOUD, as in permanent hearing loss loud.
According to JBL, the sensitivity is 92dB @1m.
That is already absurdly loud. Consider that 85db is Reference Level.
If you extend the speakers performance out to ~256 w, it will be putting out ~116dB @1m if I stumbled my way through that correctly.
(Reference Level dynamic peaks are 105dB)
What you need to be certain of is that your Amp is stable for the load:
From Shady's review here:
The JBL HDI-3800 84lb beast of a floorstanding speaker features triple 8" bass drivers and an advanced compression driver and waveguide. We review it to determine if it lives up to the JBL heritage.
www.audioholics.com
So the short of it is yes, you would be fine.