Bi-wiring with different cables for HF and LF?

If you are going to experiment using silver cables for your bass run, I'll offer a suggestion. Since silver is expensive, and you don't have your mind made up as to what will work best (I make that assumption based the fact you are experimenting), I would to borrow some silver cables if you can. Generally speaking, what people like or dislike about silver cables, tends to be in the high frequencies. For low frequencies, its very possible that using silver offers no advantage over copper.

If you try copper, as well, you may want to compare solid core vs stranded. Again, generally speaking, stranded seems to offer better bass performance over solid. Thats not the only factor, but something to keep in mind.

I don't agree that stranded copper provides better bass than solid wire.

Silver cable sound quality can be all over the map.
Use the highest grade soft anealed silver wire and it will beat most any high $$$ cables. I personally have owned or have tried in my system many of the top of the line speaker cables and I have no desire to switch from my DIY Silver 99999 soft anealed speaker cables.

Stringreen

Coherence is compromised

After more thought, Vandersteens comments, checking the Legacy site, I have to agree with Stringreen. Your speakers are voiced with well thought out crossovers to achieve max coherence. By mixing cable you could potentially effect speed, transparency, musicality and most certainly change ideal coherence through the frequencies. Will it damage anything? NO. Could it sound ok? Yes. Is it the ideal arrangement? Not close. Getting better sound is more a function of removing offensive artifacts than adding superflous components. Thank you Stringren for pointing out the path.

Yes, but for low frequencies, do the cables really need to have the same "voice" as the cables for the highs? How much "voice" can there be with low frequencies. When we talk about bass articulation, at what frequencies does that occur?

I use the same type of speaker wire as Ozzy.
I bought mine from Joe Levy at Tempo Electric, unterminated.
I also use the same in ICs from Pre to Amps.