I don't know of the issues that apparently plagued the dnn992, but as dgage said, they are as good as you'll get. In the head unit world you have Kenwood, Pioneer, Alpine, and Sony. Alpine and Sony have very few available models, Pioneer and Kenwood have a pretty robust selection. Both Kenwood and Pioneer have head units available that can run a basic 3-way active system (tweeters, mids, and subs).
I am running a Kenwood DMX906S. This is the top tier Excelon unit that does not have Nav, or CD/DVD. It has a nice capacitive touch screen (not quiet as nice as the XR line, but since it doesn't play DVD's that's not an issue), 3-way crossover network, wireless Carplay, 2 USB inputs. I have a 256 GB flash drive connected, and it compiles the entire library in less than a minute from when I start the car.
My only complaints are with regard to the interface. The home screens are too cluttered, and I wish I had more control over how they looked, but I had similar complaints while demoing the Pioneer stuff.
I've never liked Alpines head units, mostly because I they've never made a good looking one. I think the Sony's are the best looking/least cluttered, but they don't offer anything with wireless Carplay, or active crossovers. This leaves Pioneer and Kenwood, and it a lot of ways it's a matter of preference between the two.
So, my Kenwood DMX906S has some great features, works well, and my only complaints are related to lack of customization options.
My flash drive is full of FLAC files, I haven't tried anything else from the flash drive.I just bought a DDX9906XR and haven't installed it yet. One big selling feature for me is the dual-USB and the HiRes capability with DSD decoding. On your flash drive, do you have AIFF files? I'm hoping the unit will play them and I don't have to convert to another format.