After years in insurance ending as National Accounts Manager with responsibilities for group risk and starting as a grade A clerk and working my way down I feel reasonably comfortable buying direct - for many I can only reiterate what Canary Fan said.
If in doubt use a broker, buy on quality not price and use full disclosure . I’ve had to replace two full systems due to burglary . You don’t want to replace your Nova with an Atom
My hi-fi is on my home insurance with Saga, they didn’t require it to be listed as it doesn’t go out of the house, but did suggest that I take photos of the LP12 because it was so old, they were somewhat perplexed that a piece of domestic hi-fi 40 years old could still be in use and replacement cost would be over £3000. They also cover my camera equipment on my home contents and I only needed to list items with a new value of over £3000.
Also use HisCox, has a claim last year, rain damage to parts of the Hi-Fi and they were brilliant.
Whoever you are with, worth checking the policy wording for items sold in pairs. E.g. loudspeakers. Many policies will only pay out for only one item if one item of a pair is damaged. HisCox we’re brilliant, they paid up immediately for a new pair of ProAc D30s after one of them got a soaking.