Of course nobody is mentioning the elephant in the living room that Soundstream is pretty low end Chinese junk. There's a reason their "2500W" amp has an MSRP of 225$ and it's NOT because American Bass, Sundown, DC, DD, etc. are all evil and greedy.
If you had bought a high quality amp that failed you'd at least have a solid reliable amp after a repair. Now you have a doorstop that would cost you your purchase price to repair.
About the only thing you could blame on the seller is if the board shows signs of repair. IF it was blown and some rookie tried to repair it by just randomly throwing parts at it it is highly probable that it would run for a little while and then fail. Otherwise, it's most likely that it blew from being poorly designed and poorly built, using low quality parts and labor.
You will not read a story like this involving a Zapco, Audison, Zed, Sundown, AB, DC, DD, Crescendo, etc. amplifier. In fact after I read the original post I knew it would be one of these sketchy China made ones.