The LS-17 will definitely be better but the price will be much more as well. How much are you willing to spend?
The LS-5 mkIII will also be much better, definitely a killer preamp but remember, the LS-5 is an all balanced preamp, so if the rest of your system does not have balanced capabilities it will not work.
The LS-5 mkIII will also be much better, definitely a killer preamp but remember, the LS-5 is an all balanced preamp, so if the rest of your system does not have balanced capabilities it will not work.