Which 4675’s do you have? I believe they made an a,b, and c version, and they each used different drivers and crossovers, though the basic design was the same. I think the “a” version had a 16ohm HF driver (2445J) and a pair of 2225J’s in parallel for an 8 ohm LF load. Later versions used 2445H, then 2446H for the HF driver, and 2225H, then maybe 2035H for the woofers. I think the 3160 crossover would only work on the first version. You may have to pull one of your woofers to see what you’ve got.

Any way, I would pursue running a second speaker wire to the speakers. I suspect the passive crossovers are expensive because most users bi-amped, and if you do buy them, they’re not going to sound as good as the bi-amped version.