There is nothing redeemable about the Schwinn from Walmart to upgrade. (I'm going to assume this is actually one of the $200 Walmart bikes and not one of Schwinn's real road bikes that aren't bad but sell at normal prices).

So you're better off trying to sell the Schwinn, add the money to your $400 and buy something else. Let's say you have $500 after selling the Schwinn. There are some pretty good used bikes with 105/Tiagra you can get for that money, or if you look around at sales/closeouts you can get a nice new bike with sora/2200 mix.

If you do go the bikesdirect route, and don't already have aero bars for your Tri races, the Dawes Lightning comes with the aero bars. However, I really don't think you want a triple and you can't get a compact or regular double from bikesdirect at your pricepoint.