It won't matter. Even if you convert the signal to WAV the sound quality will be the same. You can't get back what's not there.
"I understand that MP3 removes what all but very-very
young ears Hrz can detect+."
If that's the conclusion you've come to, you may want to re-evaluate your system. Most people find it fairly easy to tell the difference.
"Part of MP3 is a compressed file., And if not been removed
Then I want to decode it. Like you and everyone does with
there DAC. Up-sampling. That is if you play digital music..
Buy the looks of it, I'm not sure you fully understand what's going on here. MP-3 is lossy compression. Once you make the conversion, you can't get the information back and reconstruct the original format. When you "upsample" an MP-3 file to WAV, nothing is done to change the sound quality. It's more of a trick used to make the MP-3 file compatible with WAV. The MP-3 is made to look like a bigger, uncompressed file in order to get it to play, and nothing more. If you don't believe me, its easy enough to test. Take a Redbook CD and rip it to MP-3 files. Then take the MP-3 files you just made, and burn them to a to a CD-R set up to make a Redbook compatible audio CD. Then listen to both CD's.
I'll just add one more thing. If you're using an mp-3 service and are enjoying it, you can still get better quality. You're not going to turn an mp-3 into a higher format, but like any other format, you can do things to make it sound better. For example, with a CD player, you can upgrade to a better sounding unit, or maybe add a dac. Things done to enhance the format, but not change it. The same can be done with mp-3. So if you're really enjoying the service you now have, you can make it sound better, just don't have any unrealistic expectations.