What can be done in place of a zobel at the amp level and since my amps are built to pair specifically with my speakers, can i use a zobel on the speaker ins prior to the XO for same results?
ZOBEL is Resistor-Capacitor network. In speaker design, a zobel is to compensate for impedance rise/irregularity at HF. In amplifier design it is for stability, almost similar, or work together with input filter (C), Cdom and the output inductor...
The difference between zobel for speaker impedance and zobel for amplifier stability is in the frequency they work on. For stability, the zobel works on very high frequency (above 100kHz). The R usually smaller than 10 Ohm, sometimes as small as 1 Ohm. And this must be put very close to the amplifier, not in output terminal.
Speaker impedance zobel, is of course better put in speaker (as part of crossover design) instead of in amp. At worst, when you have commercial speaker, and you want "better" load for your amp, you may want to put in speaker input terminal.
You asked why we need to use inductor, stability zobel, etc? Because it is part of the trade-off that we choose in amplifier design. If we can make the amp super stable, even with very capacitive high end speaker cable, you don't need them. Think of it as a cure... or to increase safety factor...
If you are the amplifier designer, you need to set a standard at how much is not too much. This can be seen as "phase margin" or "gain margin" or from user's eyes, the value of the capacitance (Cdom)...
From my perspective, you don't want any low pass filter that affect phase at audible range. For this, may be you need to set the -3dB high enough so at 20kHz it is still flat, etc. etc.