Based on your updated info, the Denon MC-6000 should meet your needs. You'll have to "Decks" for mixing, two microphone inputs and extra available channels for the backup laptop or whatever. I have seen these sub $600 new down to a couple hundred dollars used - so it should fall in your budget.
It should work with Virtual Dj, Mixx and Serato so you'll have a variety of options software-wise.
If you get creative, you could probably rig up more microphones to it as well - either preamplifying them and passing them through a line input or using mic systems where two mics go into one receiver and can relay a combined signal through one output. If needed, you can put the controller into a line on the mixer or put the mixer through a line in on the controller to add options. The only downside to these types of things is if you have someone filling in/helping/working for you who is not as savvy with audio equipment to be able to trace the wires, is inpatient or overall not familiar with your system there might be a learning curve leading to a hiccup in performance.
Now for the bad news...Ots... I can't tell you if you would need an update or if a mapping file is available for this controller off-hand. You'd probably want to check the specs on their website or look through the forums on that one. Ots has changed since I have used it, I honestly do not even know if there is a good way to batch convert your files back to a conventional format or what kind of quality loss the files might suffer during this process. Honestly, when I was using Ots I was using it because of the proprietary format in conjunction with locking down the computer to prevent opportunity theft (aka make it less attractive to temps to attempt to copy my library/drive). If you have links to original downloads or the Cds you may be better off re-downloading or re-ripping your library.
Side note for anyone browsing through on this thread: I'm OCD. While others laughed at me, back in the day I imaged many of my critical Cds into WAV/ISO formats etc. I then converted/ripped everything into MP3 at 320kb/s. I then duplicated the drive - the old copy went back into it's box and has been sitting in a drawer since.
Same with my video and karaoke drive. Video got ripped in as VOB or ISO. A backup of the karaoke library was also stored - old drive went back into a box in the drawer. Since 2008, many programs and formats have come and gone. I have seen Djs use Apple, WMA, MP4, VOB, AVI, OTS, some proprietary karaoke formats etc. etc. etc. Whenever you convert, you run the quality of signal/quality loss.
What I am getting at is it is advantageous to keep a master copy of your drive in a near lossless format since the requirements put on us are subject to change. If all the software moves to FLAC files in a few years - it will be no problem for me as I can dust off the original drive and run a batch convert. When some video programs stopped supporting VOB and went over to mostly MP4 this was not an issue either. I always have the option to convert to the new format, and never have to worry about converting back or reconverting something inferior. The time and effort saved by this upfront investment has been invaluable, and storage prices keep falling. Out of those that laughed at me ten years ago - I am now the one getting the last laugh as I watch some of them repurchase their libraries...
Thank you so much for your detailed response. Everyone is so helpful. Ok... I’ve decided on the the Denon 6000 mk2. It will do just about everything at my current skill level and will be there when I grow. As for my music library, that is going to take a whole lot of time to copy, convert, store and transfer to Virtual DJ. I will keep updating my Otsav PC with a backup. It looks like the Denon will work with Ots, tho since it is an older version, the mapping issues are not going to happen and there is a limit to controller usage. Virtual DJ is much more user friendly when it comes to software/hardware/file transfer.
I will use an external HD to store the music/karaoke files since I have the same OCD thing going on.
Just need to figure out which file format would be the best for storage...
Thank you again.