I'm looking at the L2501 as well. The dealer told me it would do fine with the 72" finisher and that the only way it would struggle would be if the grass wasn't mowed often.. as in every month or so.
I believe Land Pride's literature states 15 horse is needed for the 72". Granted, that could be the required PTO HP, but this setup would still work for the L2501 as the PTO HP is around 19.