Which websites list used Mercedes XXX models for sale?

Which websites are actually good for finding used Mercedes XXX models for sale? I’ve been searching for weeks and keep running into outdated listings, cars that are already sold, or dealers posting almost no useful details. It’s getting pretty frustrating because I don’t want to waste time calling about cars that disappeared days ago.

I’m looking in the US, preferably within a few hours of Chicago, and my budget is around $25,000 depending on mileage and condition. I’m mainly interested in private listings and reputable dealers, but I need somewhere that has enough inventory to compare prices, service history, accident reports, and photos in one place. I’ve checked the usual big car sites, but the search results for the Mercedes XXX seem pretty limited and full of duplicates.

Are there any Mercedes-specific marketplaces, auction websites, certified pre-owned dealer pages, or regional sites that tend to have more of these models? Also, are there websites I should avoid because their listings or vehicle history information is unreliable? I’m hoping to buy within the next month, so I’d really like to find a better search option before I give up on this model...