For 2-way speakers such as the Preludes, I would recommend the Acoustic Zen Hologram II bi-wire cables. They are specially made for 2-way speakers, and I have found them to be very good. The Oval 8s are very good as well -- quite a bit of a step up from your current Oval 12s. I have had all 3 on my Tyler SuperTowers (which are 2-way), and I preferred the AZ Holograms. They seemed to stage a little better than the Oval 8s and seemed more coherent. On my other multi-driver Tyler Signatures, I preferred the Oval 8s.
As always, let your own ears be your guide.
As always, let your own ears be your guide.