I think Blackgate NX and K series are generally accepted as the best electrolytics available. If you wanted to go real bad ass you could shunt it with an Auricap or Hovland or something, but so far I've found they sound best without shunting until I entered really high values (which as aos said is very, very expensive - be warned).
Blackgates, both standard and NX, do take an incredibly long amount of time to break in. Don't be surprised if the amp sounds loose and slightly shallow until you get into 100+ hours, even at 40-60 hours its still not all the way there (yeah, seriously). I recently went to all Blackgate NX in the low voltage supply of a project and a few in the high voltage supply as well, my amp is just now getting the bass definition back (and ******* does it extend). Have Nichicon Golds I'm planing to experiment with as well, but haven't yet.
If your buddy is going all out for his PS encourage him to experiment with different components instead of looking for easy answers. For what its worth.
carlo.