what do I upgrade?

Errm many ways... better cables (if you like nordost, go upwards), power cords, isolation, etc, or better source...

Nice System !!

If you are really feeling the upgrade bug, I would change the Krells.

COnsider Pass Labs, Gryphon, GOldmund or ... Naim (works great with Wilson)

Fernando

Power, resonance control, and acoustics. :-)

First off, you have what appears to be a pretty nice system. (If you haven't installed dedicated circuits, start there. Once you have a good system, invest in that. I just did and it made a big improvement.)

However, my question is: What don't you like about your system?

If one particular piece seems like a weak link, there is your answer.

If it were me, and I liked my system and was just looking around for something to spend my money on (and aren't we all, since this is our hobby!?), I would suggest giving analog a shot. (Again, assuming you have already addressed the power conditioning issue.)

For a few grand, you can get a pretty decent used analog setup and try it out. Who knows you might like it?!
If not, sell it. (If you guy used, you can get away without losing too much, if anything.)

Good Luck in your search!

IMHO, Your source and speakers are great. The amp is acceptable. The Showcase Pre/Pro, ehh, didnt do wonders for me in 2 channel. So that is where I would start.

All the above are correct as well. AC conditioning, room treatments, or maybe a try a few different cables... To see what you like and tweak things a bit. Though Kurt has it right. Knowing what specifically you dont like will solicit the most informed responses.