Is it worth increasing the cabinet volume?

I'm happy with my desktop speakers but never resist the opportunity to tweak. The current cabinet volume is 7 litres. I can swap the drivers into 8.3 litre cabinets but the simulation is less than impressive.
My sub's filter is 60hz 12dB octave.
Would you bother?

boxupgrade.JPG
 
Maybe not for the small amount. You could equalise it or you could use resistive damping?
That was my thinking but there's perhaps some interesting maths that's beyond me.
If 50% of the program signal is in the lower frequencies and it takes twice the power to raise the output by 3dB, doesn't the 1 dB increase offer increased efficiency?
My maths is probably way out but if you could make your car engine 10-12% more efficient you'd do it, right?
 
There are two tradeoffs you can adjust for, efficiency and cone excursion. Obviously they overlap, for example you may get more output due to cone excursion, or the ported box, and you relate that to the amplifier power used to learn what you've achieved.

to read cone excursion data
When there is no box loading, double the excursion takes double the amplifier Voltage which is 6dB and it is four times the power. The excursion plot is going to suggest how much output you'll get when comparing boxes.