OK, everyone take a deep breath!.
I've downloaded SwitcherCAD III so I can try simulating the crossover!.
So I've been having a play (I've also measured the values of the inductors in the existing crossover, as I realised one of my multimeters has an inductance range - that I've never had occasion to use before!), the bass inductor reads about 0.6mH (presumably 0.64mH?) and the treble inductor reads about 0.08mH.
I used the simulator to plot the outputs of the crossover into simple resistive loads, with the original values. I then changed the bass unit to 8 ohms, doubled the value of the inductor, and halved the value of the capacitor, and ran the simulation again - the plot was essentially identical (as expected).
I then tried changing the 2.2 ohm feeding the treble filter to 6.2 ohms, and ran it again, as expected the level dropped somewhat, but the filter function didn't change appreciably - so I'll probably try it like that and see what they sound like.
In both cases the tweeter shows a large peak around 200Hz, presumably this is partly due to using resistive loads, rather than actual speakers?, I couldn't see any speaker components in SwitcherCAD III - not that I really knew how to use it :lol: