Will lossy compression prevent me from performing audio analysis?
I would make a comment (not really sure about it) but I don't have enough rep, sorry (tell me if I need to delete this).

I just wanted to suggest trying to load the heavily compressed mp3s first, because I'm guessing matlab would decompress them to the same amount of samples and may lock up the same.

Also, if possible, I would process the files in chunks and not load them all at a time (I'm guessing matlab has a function to seek in the audio file without loading it all in the memory). You say 1.5GB each, so if there are more than a couple, you may actually be maxing your RAM (if matlab converts from 16bit to float or double, one file could probably max the ram).

Last thing, I'm not sure if you mean 8 kylobytes or bits per second. I'm pretty sure 8 kilobits per second is not gonna produce anything remotely usable.

Again, I would have made this a comment because I'm not really sure about it, but I can't :(