I purchased speakers and amp through Best Buy which is being fulfilled by Ultra Discounts Corp

Sounds like this Ultra Discount Corp is able to purchase from BestBuy at a discount for their clients. If l’m correct the warranty is still valid just the same as if you bought your  Sonos via a professional installer. 

However, I suggest you call Sonos Sales for a definitive answer. 

Honestly, I’d be contacting Best Buy, or Ultra Discount, and not Sonos. 

Return policy is likely different.

How much did you save over buying direct from Sonos? 

Based on my (not recent) experience with Best Buy, check your manufacturing dates to make sure you aren't getting old versions that may have been improperly stored for many months.

Didn’t save much at all, very close to retail.

Best Buy pushes you to ultra discount, their third party vendor, and can’t find any info on ultra discount corp which is really odd.

Since they’re the ones who are providing the warranty, and not Sonos, it does seem odd. Fortunately Sonos provides customer (not necessarily warranty) support to all owners, regardless of where the device is purchased, or how old the device is. 

It’s been my understanding for years that regardless of where a product is legally purchased the Warranty is the responsibility of the manufacturer which deals with product defects over a specified period of time.

Returns are typically regarding buyer’s remorse or a defect that can be presented to the seller within a 15-30 day window  (in the US) as a courtesy to the buyer. Beyond that courtesy window buyers remorse is gone and product defects are handled by the manufacturer.

It’s no different as when my Samsung TV failed one month before the warranty ended. I didn’t go back to the place of purchase but to Samsung. That’s why it’s important to register your product with the manufacturer and retain the original sales receipt.

So in this case IMO the Warranty is a Sonos responsibility pending any language that voids the warranty based upon how the OP made the purchase. That’s why I suggest contacting Sonos to get a clear understanding of the “warranty” period/responsible party.

Wildly disagree. Normal ‘warranty’ is processed through the place of purchase, it is up to them if they choose to go through the manufacturer’s process, or simply replace with new. It’s only after the purchase place’s responsibility ends that there is any remaining potential with the manufacturer. As I understand it.

Wildly agree with ‘registering’ the product, though. Something that Sonos handles automatically when you register a product to your account. 

Well I have to “Wildly” disagree with the first statement. Although, I haven’t had an extended need to request product service for a defect in years except for my mention of my Samsung TV. However l’d direct you to Apple regarding 3rd party warranty products sold by Apple.