Lets start with a "Welcome to the Forums!!!'
 
Now, as for your problem.  If you put the E6550 in the board, you can post correct?  From this post, can you get into the bios? 
 
As for the bios flashing process, you mentioned the ISO method.  What is not going well with that method?  Typically what users have problems with is how they burned the cd.  I recommend a program called Active ISO Burner.  When you are burning the cd, burn it at the slowest speed that your drive can handle.  There is no need to burn it fast, as the file is about 2MB and burners tend to have problems with burning small files fast.
With the E6550 in motherboard, connect just your CD/DVD drive, graphics card, power supply, 1 piece of memory and keyboard.  Reset the bios with just a quick reset.  Then boot up.  You will likely get a error about the bios being reset.  Thats normal.  Press F1 to continue and let the board start to boot up.  With this configuration of hardware (an no other drives connected) your motherboard should start up off of the CD and flash your bios.
 
Once flashed, restart the computer and be sure that it will post again.  Then power it down, change your CPU and reset the bios.  You should be flashed and able to support the new CPU at that time.
 
Good luck and post back your results please.