I can get pretty close to the Weston tone with just about any bass with roundwounds through the Rusty Box, but my Ric definitely does it best. No tweeter is another must IMO (the Rusty can get pretty harsh through a brighter cab). I haven't tried mine through 15s like Weston though
Between the Rusty and B3K I definitely am more of a Rusty fan, they actually do stack really well though (with Rusty on a low Gain and B3K on a medium Gain/medium Blend I got some really great P-bass tones). I find them to be in a similar tonal universe, and even planned to replace my Rusty with the B7K when I got one but still much preferred the tight grindy punch of the Rusty no matter how much I tweaked the B7K (which I no longer have). I actually think I can get closer to my fave Rusty/Weston tone with the DG VMT Deluxe than the B7K which I found surprising inch. Something about the way the mids punch differently.