My understanding is you want to make sure and get the LS5 MKIII not the earlier versions.
I would agree with rcprince:The LS5 will be a fully balanced design, whereas the Lamm preamp will be single ended and it has two volumn knobs (left/right) which might annoy you.
I would agree with rcprince:The LS5 will be a fully balanced design, whereas the Lamm preamp will be single ended and it has two volumn knobs (left/right) which might annoy you.