I chose a Russian cruise line deliberately, knowing it would be a more authentic experience than the more luxurious western style river cruise ships. Also Vodohod's Zosima Shashkov had single cabins at a sensible price.
I had realistic expectations of the 3-star experience: small cabins, plainer cuisine, etc.
My cabin turned out to be on the top deck, next door to a bar and the wireless router. I had internet for the whole cruise, but most of the 298 pax did not. Although small, I had plenty of storage, a small fridge, AC/heat, and a flap that lifted up under a big window for a desk. As the cabin was at the bow, I never heard any engine noise - a big plus as we sailed every night.