BillFitzmaurice.info

This on board amp from Parts Express looks good, at a price that makes sense.

https://www.parts-express.com/dayton-au ... h--300-798

It could be mounted on just about any of our full range cabs with minor modifications. It has enough power to drive a pair of 8 ohm cabs, so it would be easy enough to install a 4 pole Speakon on the cab containing the amp and one on the extension speaker. Full DSP that includes crossover, EQ and limiting plus Bluetooth makes this a very attractive rig.

Added note: the 2nd channel has a non-defeatable 1,000 hz filter. From the manual.... " The HIGH PASS output has a passive 1 kHz high pass filter. Even if you turn HPF off in this menu, the signal is filtered out below 1 kHz. The LOW PASS output can output full-range.
and ... "Filters are not affected by changing presets. Filters will never be changed by pressing the “DSP MODE” button on the amp.

That's a secondary filter, so with our cabs crossing over to the HF section at 1.2kHz or higher anyway it won't have any effect. I'm also under the impression that the DSP modes are EQ pre-sets, so you wouldn't want them to affect the crossover frequency.