First off, I would like to say that being an experienced dirtbike/atv rider with some road experience puts you in a good position. You don’t need to limit yourself to the small selection that those of us just starting out have to choose from. You can consider buying the bikes that we would be upgrading to from our first bikes.
Because you apparently want to go the cruiser route, I won’t be recommending any street-legal racebikes such as the R6 or GSXR600 to you (which might still be too much for you anyway despite your experience). Suzuki makes an 800cc “power cruiser” called the Boulevard M50 that is essentially a smaller version of the M109R, their competitor to the Harley V-Rod. It has been on the market for a few years now and can be had used for about $4k if you know where to look. It seems like a nice bike overall but most reviews say that it badly needs upgraded brakes for what it is. The Honda Shadow 750 is likely available in a trim that passes itself off as a smaller “street rod” as well, and those are fine bikes.
You should also consider looking into older Honda Magna 750s. It is a motorcycle Honda made from 1994 to 2001 that essentially combined the VFR750 sportbike engine with a cruiser frame. I do honestly believe that would be the perfect bike for you despite my limited experience as a rider due to what you say about what you want out of a motorcycle and what your past experience is. It is a sad shame they discontinued this bike in 2001, but if you’re willing to shell out money for a used bike that old (which most first time owners end up doing regardless), it would be worth the trouble.
EDIT: Though I myself am a new rider with limited experience, I have been following motorcycling for 10 years now as my father has ridden motorcycles since before I was born. When I speak as though I sound like I know what I’m talking about, I really don’t. I’m having him do the talking for me.