Help: crossover for Thiels and Velodyne sub?

I'm running Thiel 2 2s and a Velodyne F-1500R sub without a separate crossover. Each is driven from a different output on a BAT VK-3i preamp.
The Velodyne is a 15" servo/250w amp that retailed for about $1600 eight years ago (Stereophile Class "C").

The Thiels use PAD Colossus wires from a McCormack DNA-1. The Velodyne uses a long Tributaries siver-plated copper i/c.

QUESTION: How should I manage the crossover?

Should I go through the sub first, and then to the Thiels (I don't have a great interconnect to do this with though).

Or should I get an external crossover (i.e. how good is the Velodyne crossover)?

If so, what brand/price crossover should I look for?

Thanks for your advice.
(Sorry for the repeat)