Platinum Notes Worth It?

I went with the cheaper Beatunes which is similar to MixedInKey but also has a gain tool. TBH though if the file is low quality to start with it will always be low quality. I have a massive collection of music and anything below 256kbps is strictly for home use. However, the music you use will only ever be as good as the systems it plays out of, cheap soundcard, mixers, amps and speakers can make high quality music sound flat and lifeless.
It much better to start of with a good file so if you’re ripping from CD rip at the highest possible bit rate or use a music pool that offer high quality Mp3s or WAVs. Torrents are a definet no no for quality and the amount of “DJ’s(?)” that get music for them is shameful at 96kbps or 128kbps your reputation as a DJ who plays good sounding music is at risk. My moto is “If it’s worth playing it’s worth paying”
If you don’t have have to many poor quality files you could look at Sound Forge or Audacity to clean up the sound and increase the gain. It would mean working on each file individually but ti doesn’t touch the original file as you can save the reworked file as a new one. I use Audacity for my recording and as you looking for a tool to create Mashups Audacity is free
Have a read:
http://lifehacker.com/5810575/does-bitrate-really-make-a-difference-in-my-music
Have a look:
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iTunes Match would replace a lot of older files with 256 AACs for you…