Here's the setup if you are serious and want to please the Wife..
1) BMB DX-3000 Mixer
(it has a remote, and controls to prevent people from turning the volumes to the max and blowing your stuff up)..
1) Carvin UX-16 Wireless Microphone
(because corded sucks, people step on the and trip especially during parties).
1) Pair of RCF ART-312a Powered PA Speakers
<- Proper Speakers are important.. Don't try doing Karaoke with your Home Theater speakers, you'll blow them up.
1) Pair of XLR Cables
1) CAVS IPS-11G
1) 64GB USB KEY (Transcend 64GB JetFlash USB 2.0 FLash Drive TS64GJ500)
You can stuff around 25,000 songs (MP3+G) in that USB KEY. The CAVS is great, it has a MENU setup called INXMENU which gives the singer a straightforward UI to select songs (plug in 4-digit code from the Songbook). Can search via Song Title, or Singer too. It does play MP3+MCG files though (easy to convert CD+G's, or MP3+G's to MCG+MP3) to said format with the MCGManager program. MCG's are just compressed .CDG files making it take up a lot less space.
If the songs your wifey wants to sing is primarily in english, then I suggest sticking to MP3+G (or CD+G) Karaoke. Much better Quality (has background singers and such) than that MIDI sounding Magic Mic BS. If your significant other is Filipina though, might not have a lot of options - lol. Not very many Filipino songs in CDG, or MP3+G format.
If your wife really loves singing and you want to get laid 3x a week, get her this setup - lol. As for songs, you buy MP3+G Karaoke Songs from the following
Stick to "ZOOM", "CHARTBUSTER", "SUNFLY" brand.. Sound Choice has the best sound quality out of all the Karaoke Brands - they don't release CD+G's anymore but you can buy their rebranded MP3+G tracks from