320 has been proven to provide little if anything in multiple listening tests at hydrogenaudio.org over 256k at vbr. in fact, it only really makes effect if the listener knows she is listening to the 320 file: placebo.
versus lossless is up to a certain person, sample and player. some players have improper decoders and cannot do flac, alac, or even wav properly as they are optimised for mp3 or mp4.
for me, 256vbr aac is my favourite but mp3 is just fine as well. 320 i try to stay away from for the extra space as well as its really infant-size of improvement even if it exists.
but going from mp3 to lossless is pointless: you get only bigger files while not getting better quality. once shrunk to aac, mp3, mp2, ogg, mpc etc, you lose all the extra informatioin. making lossless from lossy is like filling a balloon with hot air: there is really nothing inside.