I would suggest:
1) cables first
2) pre second - if you liked tubes, you should probably give serious thought to a good tube pre and/or the Audio Aero Cd player
3) source last - Levinson 390s is quite good, but I personally do not like the 390-380-336 combo - I find it quite fatiguing - so I would break it up either at source or pre... I have found Levinson dealers are usually great about home demos, so (if possible) you should consider a home audition of the full set... and see if you don't feel tired relatively quickly too...
Good luck,
Jacob
1) cables first
2) pre second - if you liked tubes, you should probably give serious thought to a good tube pre and/or the Audio Aero Cd player
3) source last - Levinson 390s is quite good, but I personally do not like the 390-380-336 combo - I find it quite fatiguing - so I would break it up either at source or pre... I have found Levinson dealers are usually great about home demos, so (if possible) you should consider a home audition of the full set... and see if you don't feel tired relatively quickly too...
Good luck,
Jacob