Sumo tournaments September 2013

hello,

My husband and I plan to purchase tickets to the upcoming Sumo tournaments in Tokyo.

We want to watch the semi-finals/finals,
but I've been told by the people at http://www.buysumotickets.com/ that they don't even try to purchase box B/C tickets on those days because it's nearly impossible to obtain.

My dilemma is as follows:
should I go for arena A tickets on the semi-final/final day,
or - should I go for box B/C tickets on a regular mid-tournaments day (specifically September 26th which is day 12).

which do you suppose will supply the better experience?
I would be happy to get your advice on the matter.

Also, if anyone knows a method to obtain box B/C tickets for the semi-finals/finals in advance (even via Japanese websites), I would be happy to hear.

Thanks!

As far as I read the official site,
http://sumo.pia.jp/sumo09.jsp
all tickets can be bought in advance.

But the first reservation lot has already finished at July 22th, so the final and semifinal tickets could be already sold out.

If there are the tickets left, there will be another reservation lot, I think.