Danube Cruise 7 nights advice/tips

[200Plus Club]

Looking at a River cruise next year, particularly interested in a Danube cruise. Having watched a few you tube reviews it seems that Viking were well regarded if a little pricier.
Anyone care to share experiences please of their Danube cruise, and which company you'd recommend etc?
We'd prefer to go in milder temps than the hottest months so any relevant advice would be appreciated.
Many thanks