I had my right flipper end stop fall off the other day after 6 months of play, I put it back on without loctite but will use some if it happens again, I checked the left and it seemed tight.
I upgraded my speakers with those Pioneer ones also after reading the Pinside thread, what amazes me is how much better these US$30 speakers sound and how rubbish the speakers that CGC supplied were, I wonder what they paid for them in bulk about $10 a pair? it would have been nice if they came with speakers that were up to the task already.
I have not wired up a sub yet but I'm on the lookout for one secondhand and local, so will grab one soon.
As for the Stereo question it's something I didn't think of when I wired mine up, but glad to hear that it's OK as it is.....I don't know if it would be possible to tell the difference between stereo and mono anyway with the speakers close together and the position when playing.
Yes, the speakers are a big improvement and the subwoofer will really make the sound pop. I can't remember ever having a flipper coil fall off before it happened on MMr. I would like to blame it on the shaker; however, the coil sleeve in backwards did not help and my other pins have a cointaker Red Tremor shaker in them that is much more violent than the MMr shaker, so I don't know.
I suppose they keep putting in cheap speakers (probably more like $5 for a pair in bulk) because pinball historically was put in noisy arcades where you really could not discern much sound quality anyway, so why put in good speakers? Most of these machines are for home now.
A nice LE option would be factory installed Polk, Harmon, JBL, etc backbox speakers with a built-in powered cabinet subwoofer to replace the unpowered subwoofer along with a headset jack port. It would not be hard to do and would have great sound without having to place a subwoofer below your machine. Might add $150 to the actual cost of the machine maximum.