my view on this is that the only way to go is termi, here is why, you get an italian bike and basically i think you should put on what is really teh italian exhaust that seems to "go with" the bike the best.
personally whenever i see a 748 that i want to buy with any exhaust other than termi, in a way it turns me off, for me personally the termi sound is the best sound out of alll the other brands.
can you put on other brands? of course, they are all made very well, but for some reason its just not "right" without a termi system on a ducati. taht is my take on it.
WOW--they did a great job with marketing didn't they...?