How does the VPI Aries II stand up to current mid priced tables?

Use the Walker Speed Control. It works great on my VPI Scout II. Love VPI. The upgrade path on these is an audiophile tweeters dream.

The Aries 2 is a good table, but the cost to upgrade it with a current model platter and/or tonearm is cost prohibitive and would have been better served by investing in a more up to date model. A speed controller would be a worth while update. 

Just to ad to add to the conversation, in my speaking with both Harry and Matt at VPI when I was inquiring about moving from my VPI Aries 1 table to one of their newer ones  they both first asked what platter I had on mine and and the serial number, after that they said to keep the Aries 1 table as it has the best platter and combination of items that they cannot duplicate today and if so the table would cost in the $9-$12k range.

Is there a drop in platter upgrade for the Aries II?

The VPI Aries 2 also was produced as a "Black Knight" edition, which is the one that I've been using for many years.  I've tweaked it a bit over time.  This one has a black acrylic platter that I think is a bit lighter than the standard Aries 2. It came with a 9 inch arm, but early on I switched it out for a JMW 10.5i Classic 3 tonearm with new custom arm board from VPI, which made a nice improvement. I consider the speed controller to be essential for this turntable. I use the VPI SDS version, although I've heard good things about Phoenix and Walker speed controllers, as others have mentioned.  Various Dynavectors worked well on this setup, although I've recently upgraded to a Lyra Kleos SL, which is outstanding.  Would be interested to know how you like your newly acquired Aries 2 . . .