I hope you don't mind me adding my $0.02.
I've been hosting karaoke since the 90's. I have made the conversion to digital. I still purchase CD's and use Audiograbber to convert them.
I have over 45,000 songs. Out of these, I only have about 21,000 unique titles. I print my books without a reference to the manufacturer due to space constraints. My books look very professional with heavy laminated covers and plastic binding combs. However, even when I only print about 21000 songs, the books are quite large, requiring the largest comb binding.
I use RoxBox for karaoke. I tried PCDJ KJ Pro, but I had issues when I upgraded to Windows Vista and I never bothered with it again. RoxBox has been rock-solid for me, and I've been using it for about 5 years. One of the reasons I purchased RoxBox was their built-in book creator. I can choose to include/exclude duplicates and I can choose to print Disc reference or not. But with the large collection I have, I've opted NOT to print them out. I do have MULTIPLE books (usually 4-5) at a gig. Surprisingly enough, most people prefer the books by artist, so I have more books by artist than I do by title.
When a singer makes a request, I usually will select what I feel is the best version of the song they want to sing. No, I don't know all 21,000 songs, but after 15 years, I can usually guess which brands are better. If a singer asks me for "another version" I am happy to accommodate their request. Most of my singers trust my judgment, but some are married to a specific brand and/or song.
If a singer asks me which version of a song I have, I will show him/her. They also love to see the screen and see all I have going on.
As far as the key changer... I use Pacemaker and I don't have problems with it. HOWEVER.... I always avoid doing a change of key beyond 2 steps. After that, it really sounds like CARP. Yes, I misspelled that.
If a singer insists they have to change the song more than 2 steps either way... I will do it, but I will let them know that it will change the sound fidelity tremendously. Especially with subs and a bi-amped sound system. I also have my key changer configured to change in full steps, not just half steps. This helps tremendously, because I always divide by 2. They want it down 4, that's -2 in my system.
Now, I agree that the rest of the equipment is substandard. There's no excuse for not having a professional (even a simple behringer) multi-channel mixer with effects and multiple microphones. To me, the addition of a singer's audio monitor and the multiple wireless microphones is one of the best things about my sound system. I never hear a complaint about a singer not being able to hear him/herself... and I run them through a separate mix, as an AUX out.
When someone brings me a CD, I ask them if they are willing to use one of my versions of the song. About 50% of the time I already have it. When one of my regulars brings a brand new CD that I don't already have, I rip the track they want and add it to a special folder that I have reserved for them. The song doesn't become part of my collection. It's something I do to accommodate their requests. It's rather time consuming and I'm trying to avoid this in the future. Therefore, I'm considering buying an inexpensive vocopro dual CD+G player for this.