This is still recoverable. When it wont power on at all, your goal is to get the "red text" to show up. From there, you can get to DL mode. I am guessing you had a voodoo kernel installed when you flashed? If so, you need to put a checkmark in the repartition box on Odin, or this can happen. I have been here a couple times, and it is not a brick.
This is going to sound like magic, but it does work.
Connect your phone to your USB (rear port).
Open ODIN up
Remove the battery
Insert the battery
Press and HOLD VOLUP and POWER until red text shows up
Now, hold both VOLUP, VOLDOWN and POWER.
Wait for the screen to go dark and release the POWER button while still holding both VOLUME buttons down.
DOWNLOAD MODE.
I recommend NOT using the one-click ODIN. There is a re-partition checkbox on the real Odin that you should use if coming back from a voodoo kernel as well as a version of stock that includes the 3 button fix. If you need help finding that, I can try.
Good luck.