I prefer two speakers in order to simulate the separation of parts that exists when you listen to an actual combo. I use a Behringer UltraMizer Pro to enhance the sterio separation of parts. I believe the effects on the X4 require sterio to be fully realized. The consensus in past discussion on the topic of sterio vs mono seens to be sterio, although some use only one speaker.

I also believe that the consensus is that speakers on stands are preferrable.

I am not a professional - only play about 5 to 10 hours per week between practices and appearances. I have found the X4 reliable.
I had the X1 keyboard before the X4 came out and it did lock up on me a few times, but I think the problem was with the contact adjustment in my Excelsior accordion. Can't recall if the X4 has ever locked up on me. By "lock up" I mean the the unit had to be turned off because is was stuck on one note or chord.

I suggest you look at past posts on these questions to see what other opinions are. There are many professionals who are kind enough to take the time to post to help out the non-professionals like myself. They have much more experience than I have had.

I think I should answer your reedless accordion questions via e-mail. I notice you didn't post your e-mail. My email is rjmiller@bevcomm.net. Send your address and I will reply. If you don't have e-mail, find someone who does and send me your address and I will send a reply by overland mail.