I've still got a pair tucked away at the back of my study. They are OK. Quite full sounding and surprisingly good at soundstaging but they do lack in the rhythm stakes. Their biggest flaw is that they never quite get the feet tapping on more rhythmic music.
They work best with a warm-ish amp like a NAD. Partner with anything brighter and they start to sound a little grey.
I've got a pair of 9.1s as well. The 9.1s are the better speaker IMO. Park them on a pair of Atacama Nexus 6 stands and you'll get much better sound than the 8.3s would give you.
Ideally you should seek out a pair of used Quad 11Ls - the original one. They would be the perfect partner for Quad amplification and are certainly a worthy upgrade from the Diamonds.