I concur that the Honda products are great choices for towing '4-down' and that not having to deal with a tow dolly at your destination or storing one when you are not traveling is another great benefit of the 4-down configuration. To stay under 5000 pounds you will need to select a smaller vehicle and that might limit the ride quality/features of the Dingy itself. Still, there are some good choices both new and used. Motorhome Magazine publishes information each year, and the Family Motor Coaching January issue has a good run down as well. Honda's CR-V and Fit are both rated for flat towing. Automatic transmissions and all wheel drive tend to limit the choices a bit, hence the preference for the CR-V by many coach owners...
My 2007 TourMaster has a higher tow rating, so we use the Acura MDX model of SUV as a toad (it is right at 5000 pound curb weight with full gas tank...) Too bad that Honda/Acura changed the ratings after the 2005 model year and they no longer recommend flat towing of this model. That is why I specifically sought out a low mileage used 2005 MDX in great condition when I was buying a toad for behind my TM.
I use RoadMaster equipment (tow bar, air brake supplemental braking, tow shield...) because they are a local manufacturer. My research found that independent dealers are the best price, Camping World is hundreds more and the large motorhome dealers are the most expensive for buying and installing this type of equipment.
Base plates (the attachment points at the front of the car) are very specific to the model and year of vehicle being towed -- so research and select carefully. Installation is detailed and must be done by a trusted vendor -- if you are skilled at mechanical repairs you can do it yourself. Just remember that road safety is paramount and choose accordingly!
Chuck
PS Here is a link to instructions for installing a typical base plate:
http://www.roadmasterinc.com/pdfinst/3141-1.pdf