Cables for Harbeth-Luxman match?

In my experience the C7's are not particularly sensitive to speaker cables. I would look at decent, low cost cables that are easy to work with and explore spending the difference on system improvements further up the signal chain. It is very hard to make the Harbeth's sound bad and I got great sound with them using a variety of different cables at low and moderate price points.

Is there a problem with what you have now? It looks like it would be a good match.

Not sure what you don't like about what you have? I own C7's being driven by SET 845 tubes. Tried a number of cables - Kubala Sosna, Audience, Cardas, Kimber, Audience, AZ. Finally settled on Auditorum 23 interconnects and speaker cables. Works very well in my system.

I disagree that C7's are not cable sensitive. Perhaps not as much as some brands, but you can certainly change the tonal balance dramatically with speaker cables. Perhaps it has something to do with the quality of the amp driving them?