There are multiple threads on this. Do a search on Google for Harpcolumn + harp car or something similar, and I think you will find them.
In the meantime, as I recall, people love the Toyota Sienna van, Dodge Grand Caravan with seats that stow, and I think I read that a Volvo wagon was nice. My teacher loves her Ford Taurus wagon, but it’s older and not made any longer. I got my concert grand Camac into my Subaru Outback with no problems, but that car recently died. I bought a Honda Element as a replacement, and it fits quite well in a couple of configurations (the Honda E has removable seats, and seats that go flat and flip up to the sides of the car and clip. I love the possibilities of this car. It went in without a hitch…..no carpet so it slid in really easily.