Whenever you cascade amplifiers in a system you want the output of one stage to be a low impedance and the input of the next stage to be a high impedance. That way the stage you are driving won't load your source down.

Per the specs above you have a factor of ~40 between the impedance of the pre-amp and the power amp so you should be fine.

Not certain about the reference to impedance mismatches? Are they talking transmission line mismatches, which is a different topic? Or not mixing power amps with wildly different input impedances? For example if you are using a power amp with a FET input it can have an input impedance in the MOhm range which will load your pre-amp differntly than your 23.5 KOhm input amp. Mixing amps like that would have an effect but I'm not sure how significant it would be.

32dB gain isn't bad if that means the whole amp. Based on that number I'm guessing you have a 250 Watt into 8 Ohm power amp?