All audio components are different, different Brands, different models. However it is VERY frequent in high-end audio that 10 unit of the same brand and the same model yield 10 different sonic results. So do not buy a specific model but rather a result from a specific unit.

There are many reasons why the same models sound differently:

1)  Companies do not care or do not know what they do.

2)  Very low quality control

3)  Some companies, since a product get some reputation, secretly degrade sound and quality of products to pursue economic motivations

4)  Small production companies source parts “production run by production run”. In many instances the past are different or changed run by run

5)  The assembling techniques vary run by run, employee by employee.

6)  Components age with different past while they are used

7)   In some cease is it too costly to tight-control some critical parameters of elements and it “made as is”

There are many other reasons but the key is to remember: it is highly possible that any given model has a unit of better vintage.