ONLY 300 Watts??? That's a ton of power that should drive almost any speaker available. Just as an example, back in 2009 Kal Rubinson ran the 802Ds with the lower powered CA-5200 just fine (https://www.stereophile.com/musicintheround/music_in_the_round_36/index.html), so I'd be shocked if your 5300 didn't have plenty of juice to fully drive 800s without biamping. The 800s are 90dB efficient but do drop below 4 Ohms through a good part of the midrange, which does make them more difficult to drive. But here's a quote from the Classe website regarding your amp:
"* Specifications for output into 4 ohms are omitted because the AC Mains/power supply cannot support all channels driven simultaneously at this level, which would require over 5,000W and only occur under a special test condition. The amplifier easily drives lower impedance loads."
Translation -- your house will run out of juice before your amp does. Suffice it to say I think you're worrying needlessly over the power issue. You have a beast of an amp.
"* Specifications for output into 4 ohms are omitted because the AC Mains/power supply cannot support all channels driven simultaneously at this level, which would require over 5,000W and only occur under a special test condition. The amplifier easily drives lower impedance loads."
Translation -- your house will run out of juice before your amp does. Suffice it to say I think you're worrying needlessly over the power issue. You have a beast of an amp.