This is

Here is my system:

Helikon and Benz M2 (Cartridge)
Aries T/T with 10.5 VPI arm
Cardas Natural IC Tonearm cable
ARC PH3 SE Phono (stock tubes)
ARC LS 25 mkl (NOS Sovtek)
ARC VT 100 mkll Power amp (drives top)
Perreaux 2150B amp (drives woofers)
Infinity RS 1-B Speakers (modified and xover moded)

My IC are (besides the tonearm cable) Acoustic Zen: Silver 2's and 1's and Matrix 2's and 1's
My speaker cables are AZ Satori

Where or what should I focus on next? What should be my next upgrade or purchase???
Wow, good setup! Looks like the next step is to decide what finer points of the system you wish to bring out. For example, do you need a warmer sound, more resolution, more slam, or less of the same? You may consider trying the best cables (cost no object) from Tara, MIT, Nordost or Cardas. I would also consider a high power ARC tube amp on the bottom... do you feel the Perreaux may be a bit fast and aggressive? Or perhaps going dual mono? The best sound I ever heard were your speakers driven by ARC 300 watt monos.
Good Luck.
Vinyl baby...more and more vinyl!!
You have great stuff, now you need to get into some isolation/damping from vibration. I use and find the Bright Star Audio products to be of great benifit in my system.(start with the TT, Big Rock, Air Mass combo, then do the phono and pre with the same combo, next a Big Rock under the VT)

The next thing would be to get some great power cords and address any AC power issues you may have.

Thirdly do some room tuning, ASC tube traps can do wonders.

You don't need to do it in this order. But do it before you change any component or cable. You don't know what you have untill you do some of these things.
sorry folks.......the title of this thread should have read the above!!!!
....This.......What is "the Best Upgrade Question".....