Cabling Question

Anyone with experience cabling Monitor Audio speakers with tube amplification? I have MA GX100's running on an ARC VT-130SE/LS-16 (both with GNSC mods) combo (the rest are an ARC CD-2 and an ARC PH-3SE/ VPI Scoutmaster). Tried Kimber 8TC full range, Audioquest CV-4 bi-wire, and XLO/VDO bi-wire cables. Can't hear difference betwixt Kimber and XLO's, Audioquest were not satisfying. Wondering if anyone could shed some light on cabling for MA ribbon tweeter speakers run with tubes. The MA's replaced a pair of Celestion SL600's. You can surmise from my equipment that I don't change gear for fun, or often. Demo-ing at home is a problem because I live in the vastness of Maine...and I live in the sticks of the vastness of Maine. There are no audio stores. I don't mind buying to try, but a gentle push in the right direction would be appreciated. Money limited to about $500, used is fine. I listen to many different genres, but judge my system mainly on female vocals and string-based music.