Day Trip from Fukuoka to Mount Aso

Dear all,

I'm trying to determine whether it is possible to do a day trip from Fukuoka to Mount Aso by public transport, but I'm having a bit of trouble understanding the various timetables for the two trains and the bus that I would need to take to get to the volcano.

Based on the information in this guide, it would take around 4 hours to get from Fukuoka to Mount Aso:

http://www.jnto.go.jp/eng/location/rtg/pdf/pg-704.pdf

Is there a quicker way to get from Fukuoka to Mount Aso? If not, is Mount Aso worth a minimum 8 hour round trip to visit? I would like to see an active volcano while in Japan, but I'm concerned that I could end up spending a total of 8 hours travelling to and from Mount Aso and it may not be particularly impressive.

Thank you for your assistance.

The linked page is out of date. Below is the up-to-date access information after the full opening of the Kyushu Shinkansen:
http://www.japan-guide.com/e/e4551.html?aFROM=2161_4550

Thank you for your help.

The additional information was appreciated.

Thanks again.