Yeah, you are WAY overthinking it :). Karoake is super easy nowdays, even web based solutions exist: http://www.karafun.com/flash/?song=48052 All you need is a laptop and a decent sized monitor, like a 23"
Karafun. You can use them while being online or sync a number of songs for offline depending on your subscription with them
There are 3 tiers of subscription with them.
Party Pass - £4.99, Lasts for 2 Days, Unlimited Karaoke Tracks while online, or sync 1000 for offline.
Monthly, Same as above, but for £6.99 a month
Pro Subscription. Sync the entire library (20,000) (Cost not listed)
I've used it before for some staff parties where I used to work. It works, software is basic, but works well. Karaoke tracks are all very good. I used it with a internet connection,
Like I say, I only used it for a staff party, Karaoke is not my business, but it seemed good. I did not pay for it or anything, the party organiser set it up, so I cant comment on how much the pro subscription cost.
Use a laptop and just download the app at Karafun. For a fee, can can have access to their very large and good database of songs. You can run an HDMI out of the laptop and run it through your TV and run the audio out of your laptop or TV.
From the manufacturer's mostly Sunfly, Zoom, Mr Entertainer etc. Check any of their sites for discs. For someone who wants to do this on a computer and pro level quickly you can download the free app Karafun.com A pro license can be bought for shows and they have their own online database. Another resource for songs is karaokeversion.
Use this program. You have to get the lyrics online. Just synchronize the lyrics to the music by tapping the space bar. If you want to save to a MP3/CDG format, use this program http://www.powerkaraoke.com/src/prod_karaokecdgcreator.php
If you wish to save to a mp4 or AVI movie file, use http://www.powerkaraoke.com/src/prod-karaoke-video-creator.php
and a free program to play back either http://www.karafun.com/