I have Progressive. I needed insurance fast and they were willing to insure a 50 year old Alberg 35 without a survey. Have not had a claim which is how you really test an insurance company but they seem ok.
You might be able to add a Ranger 24 to your homeowners or apartment policy. I generally suggest finding a local insurance agent or broker, with marine experience, to work with. Policies are not all created equal and what liabilities they'll cover can vary greatly. Imagine finding you need that coverage after damaging one of the expensive boats you reference and learning you didn't get that particular coverage?
Also, insurance laws are governed by the State. Soliciting experiences outside your own state will be inapplicable, even if the same national company.
We currently have Progressive and have also used them in the past on two previous boats with liability only. We've never had a claim, so I can't comment on their performance, but customer service and prices have been very acceptable so far.
You can try InsuranceForBoats.org for more general info and links to several boat-specific insurance providers.