what about crossovers? can they "partially" blow as well? is it obvious when looking at it?
i hear measuring components in circuit yields meaningless results
Crossover caps are most likely to go bad from excessive voltage and they have a voltage rating on the wrapper. If they weren't intended for high power, the caps will be rated for 25V, 50V for higher power systems. If a cap goes bad, it can burst and there's no question when that happens.
If you have a multi-meter, separate the cap from the circuit and measure for resistance- if you see continuity, it's shorted. You should see a brief reading, but it should go back to reading OL (the most common reading on a digital meter for an open circuit). Then, reverse the meter's leads on the cap and test again- it may show the same as the first test and should go back to OL.