I think the way to go now with these is to have them working, as well as they do, and then have a hidden bluetooth amp. There're tiny, no money, and very good.
Jay made a picnic hamper into a bluetooth speaker to have on the back seat of his Flamina Touring, and I guess also useful for picnics.
We've got an old guitar amp or keyboard amp that was bought on ebay, turned out to be broken as far as intended use was concerned, then I added a little amp and transformer to use as a bluetooth speaker in our bedroom. Its the sort of project that can be done for under £20.
Our flavia originally had a single oval speaker in the centre console. I'm planning to put an oval in the front for the period radio (thankyou Brian Hilton!!) then a couple of other speakers either in the side of the console or under the dash for the hidden amp. Fair bit of other work to do ahead of that but that's the plan.