A direct coupled preamp is not going to blow out any speakers unless the power amp is also direct coupled. Chances are that the preamp output goes into an input capacitor of the power amp, so you will still be ac coupled regardless of which preamp output you use. I would go with direct...who needs two capacitors in series?
DC won't burn up speakers any faster than AC, but you would not get the audible warning that something bad was happening. However, direct coupled amps that I am familiar with include circuitry to detect this fault condition, and turn themselves off. Some AC coupled amps (particularly pro sound amps that are often driven very hard) also include protective circitry.
And then there are speaker fuses.
DC won't burn up speakers any faster than AC, but you would not get the audible warning that something bad was happening. However, direct coupled amps that I am familiar with include circuitry to detect this fault condition, and turn themselves off. Some AC coupled amps (particularly pro sound amps that are often driven very hard) also include protective circitry.
And then there are speaker fuses.