So, uh, what is meant by "remastered" here? Is it an actual different arrangement and recording of the songs? Because I don't see how you could remaster an 8-bit 28KHz soundtrack to be anything other than an 8-bit 28KHz soundtrack...
You could take the .MOD and run it through a higher quality renderer. The biggest improvement would be using high quality resampling, as the resampler in Paula is very low quality. This should improve all pitch shifting or pitch related effects. You could also render to 48 kHz, which might improve things a little bit for those samples that are getting pitched shifted up enough. You would also render to 16 bit, but that wouldn't actually give an improvement over what you would be hearing out of an Amiga, it would just make sure it's as good as the Amiga.
To get an improvement from there without messing with how it should sound about the only thing you could do is hope you had higher quality versions of the original samples around (16 bit, higher sample rate). That could make a big difference. Who knows how likely that is though.
Anyway, I'm not sure you should label what's being sold here as HD audio, especially if it's provided in MP3. Really "HD" audio is a term that shouldn't really exist, but don't get me started on all that ... best you should shoot for is remastered to "CD" quality.
