Our friend who have replied just before me, referred to a very good feature of bi-wiringbi-amping, which we are able to use different cables with their own characterestics.
But in terms he claimed that usually there's no difference obtained after bi-wiring entry level loudspeakers, I should mention that I have Wharfedale Pacific PI10 bookshelf speakers for 11 years which were not expensive at all and I am using them bi-amplified, comparing to used by one integrated amp. the difference is obvious on every matter and the sound steps on higher degrees of quality, control and even transparency, but I have not tested them bi-wired yet with one amplifier. In your case I'm sure you'll obtain benefits from just bi-wiring your Diamonds 9.1. I have listened to 9.1 on my system, main characters of sound were equal to my Pacific version, so I have to say with confidence that you are doing the right thing on your 9.1s.
Morover I also have Denon M38 connected to pair of bookshelf speakers with higher quality than Denon default speakers and the result is quite satisfying, so this version of Denon is also tested and is happy to accept good quality bookshelves.
So don't hesiatate and enjoy.