Bi-amping requires 2 amps plus an active crossover adjustable to meet the frequency, level, and slope of the original passive design. The benefits are many, most notably a 6dB increase in dynamic range and better woofers control by eliminating the series LP inductor(s) and it's associated resistance from the equation. The drawbacks are of course cost and the potential of accidentally bypassing any shaping network elements. To avoid the latter, the biamp insertion point must be prior to the shaping network, or the shaping network simulated by a DSP prior to the associated amp.
So called 'passive' bi-amping, feeding both LF an HF full range and still maintaining the stock passive crossovers is simply a waste of money. It maintains all the drawbacks, eg cost and complexity, while providing none of the benefits of actual bi-amping.