Hi Ian,
For full range on the AKSonics, which are 87dB/watt/metre, I would not recommend going to the 25W AKSA. Maybe 40W, yes, but not 25W. As Chris remarked, there are moments when the extra power is required, nice to know the grunt is there.
If the AKSonics were 94dB/watt/metre, then I'd say yes, go right ahead.
Now, on the cutting of the timber, you really need someone with woodwork skills. My suggestion would be to look around your children's school staff/fathers/mothers, and enquire if anyone there is a competent carpenter and if so can you 'hire' them for half a day. They might even have a better sawbench than a Triton, and you will have a point of common interest - your school and your children.
There is a huge wealth of talent in the general community you never find out about unless you ask. Most people are delighted to speak if asked; they seem pretty quiet until someone shows interest......
Cheers,
Hugh