“If I buy 2 can they be linked for a right and left channel?”
(Answer): They can be linked by L & R channel by line in but not Bluetooth.
“How far from the amp will the Bluetooth connect?”
(Answer): The Bluetooth distance is about 10 meters without obstacles.
“When in the Bluetooth mode can I get the signal out thru the XLR out?”
(Answer): The Bluetooth feature is for a single speaker, not two. However, when in Bluetooth mode, you can get the signal out thru the XLR out to the other (mono out).
“On the STPA3L-400D plate amp does it have a built-in crossover at 2500hz?”
(Answer): This amp. has a 2-channel amp. (bi-amp), one channel powers the HF and the other channel powers the LF; it has crossover 2.5k Hz built-in.