Hi Stewart
Its very useful to get a recommendation because car stereo has changed so much recently. I have a mechless stereo as I don't use CD's anymore and was amazed at how little car stereos weight these days, though I would expect a bit more weight for your new expensive Pioneer unit!
I also had visions of photos of you fitting some kind of large wooden enclosure in the footwell for the subwoofer but I now see that you can buy slim self contained units which fit under a car seat .....but maybe not a Morgan seat?
The underseat rails are too narrow for all the compact subs I’ve looked at so I’m going to fit my Pioneer TS-WH500A sub flat upright against the firewall in the passenger footwell - it fits perfectly
In my last Mog I had a similar sub fitted there with a false panel infront but it shortened the footwell just a bit too much so as I’ve got black carpets and as the sub is plain black with a black grill, I’m not going to bother with the false panel. I’m just going to glue some black acoustic carpet to the top and bottom of the unit either side of the speaker grill with some Dynomat behind the existing carpet
It’s only 60mm deep so it will be fine for passenger leg room and won’t be seen