The real question you should be asking yourself is this: how hard will it be for the competition to change direction or spin-off a new line to solve the same problems we have identified but which can leverage their existing market presence?
If it is easy for your competition to copy any successful niche you identify then you are probably in trouble. This is not to say that the venture is doomed, because there are lots of good examples out there of entrepreneurs who have followed this route (e.g identify problem in market, introduce solution, profit) but unless you can build your brand identity quickly or tie your competition's brands to the problems you are solving then you may have trouble.
Seriously, how hard would it be for either of the big players to offer a new line from a different shirt supplier? Given their existing market presence they might even be able to convince people to pay a larger markup on the upsale to the quality goods than you can get by only offering the good stuff.
If it is easy for your competition to copy any successful niche you identify then you are probably in trouble. This is not to say that the venture is doomed, because there are lots of good examples out there of entrepreneurs who have followed this route (e.g identify problem in market, introduce solution, profit) but unless you can build your brand identity quickly or tie your competition's brands to the problems you are solving then you may have trouble.
Seriously, how hard would it be for either of the big players to offer a new line from a different shirt supplier? Given their existing market presence they might even be able to convince people to pay a larger markup on the upsale to the quality goods than you can get by only offering the good stuff.