At or above Suit Supply level?
Lets get real here. Spier and Mackay is a bargain brand, there is a reason why they are priced at where they are. I applaud them for that but you getting what you pay for. A value suit that will do its job. Its good if you get them on sale. To compare it to Suit Supply is laughable.
They are good for what they are but lets not go too far here.
On a positive note their shirts are great for the price.
In my opinion, S&M is priced under market value for quality. I have no experience with their suiting or jackets, but I have many of their shirts.
Correct me if I'm wrong, but it seems that you are under the impression that SS has high quality fabrics and construction. I would say they are mid range, and probably the best you can do at that pricepoint in the US with minimal risk.
@Claghorn has multiple jackets from SS, as well as bespoke. I am certain he is well-qualified to assess the quality differential.