Good catch, also, did you notice his 110 dB might have been inflated a bit because those speaker's actual sensitivity would likely be less than the advertised 91 dB, especially if the impedance is more like 4 Ohms than 8, if it is anything like the V3s? And he entered 5 speakers, THX' s ref level is for one speaker. I think basing on 2 speakers may be reasonable but 5 seems extreme.
I am a believer in a lot of people can do well without external amps but to be on the safe side I would still recommend a 200 W/300 W 8/4 Ohms amp for his big towers in case he might want to crank things up occasionally.