chris-L :
Yes it is "safe" to put those in. They are above the minimum 4 ohm load the Pioneer receivers require, assuming you have only 1 speaker cabinet hooked per side. Yes changing the woofer's impedance will change the crossover point but it shouldn't necessarily damage the crossover itself. What is more likely to occur is a change in tonal characteristic from the different speaker within that cabinet. That may
be good or bad depending on your taste. But it should be "safe" in terms of your original question. 8" is small for a woofer if you
are trying to play this real loud. not sure what happened to your original woofers, but watch out that you don't apply so much power that the woofer cone excursion gets too far and hits the magnet assembly as it moves in/out. I've seen lots of speakers damaged that way. Also,
I've changed lots of speakers with non-original drivers so am familiar with your situation. again it is "safe" to put in the other woofers if you elect to, as long as you operate your Pioneer amps reasonably.
Thanks for the reply Chris, Paradigm refers to these 8" speakers as mid/bass woofer and they are the original size, The replacements are very close in spec. just a little newer, both from Paradigm, same size, with a little more wattage, but different ohm.
The crossovers are are fairly close, the replacement speaker uses a 2.0 khz crossover and the original cabinet has a 2.3khz crossover. Not sure if this is relevant, this is where I put my noob hat on.
Even the internal volume of the speaker cabinets are similar based on the brochures.
Thanks again for the reply Chris