Discjuggler burns to multiple burners, how many is dependant on your license.
I use imgburn to burn to two writers at once all the time, i just launch another instance, i never burn the same image or files though, but you can if you want i just did a test.
Usually this will(depending on how many burns you do) sooner or later give an exclusive access error, but afaik this can be ignored(im sure some will disagree;)) or even turned off in options.
LUK if you read this, id like to thank you(and your testers) for imo the most reliable and all around best burning app there is atm.
Edit: forgot to say my burners are of course on separate ide channels and my hdds are sata and i use SPTI