audiophiles who are just getting the itch to upgrade

@phill55 You are asking about upgrades to the Linn that have quite varied price points. A Lingo 2 power supply used is about the same price as the Karousel bearing, whereas the Keel chassis is about three times the price of those two ( if new). 
Since you already have a power supply upgrade ( the Herc board) although not that great, it is better than the stock power supply. Therefore, to my mind the most potential for better SQ comes with the bearing...and that is the Karousel upgrade. A lot less $$ than the Keel and a major part of any LP12. I am going to look into the Karousel myself, and i just updated my LP12 with a brand new Cirkus a couple of years ago! The Cirkus upgrade was very easily heard and a BIG uptick in SQ. 

@phill55 Just noticed that the new Karousel bearing probably will not work with your Herc power supply. It certainly won’t work with Valhalla and I strongly suspect that the same issue will apply with your Hercules!
Before making a purchase commitment to Karousel, I would check this out with your vendor. If the new bearing won’t work with Hercules ( now pretty sure it will not!), then the next step would be to look at a power supply upgrade...meaning take a look at Lingo 4...or Lingo 3 and then go to Karousel.

Thanks for all of your input daveyf. So help me understand why I wouldn't look at other turntables; used VPI or SME, etc.? I am into the Linn LP12 for $1,900 (bought used) with Koetsu black cartridge ($1,200 used). If I buy a Lingo 2 or 3 used @ $900, then Karousel bearing @ $1K then look buy used Linn Kore @ $850, I am into the turntable for $4,650 - $5850 including the cartridge. At this price point, I have to believe there are other TT's out there at this price range used that would be as good if not better than Linn? Any comments to the community? 

I’m a long time LP12 owner (since the 90’s); I really like my table, and it’s had updates over the years- I started with the Basik power supply, Rega arm and a Linn K9; now I have a Lingo power supply, Kore chassis, Ekos II arm, and Arkiv B cartridge, plus, a Trampolin and Silver T cable. I know there are other great tables available, but I’m not changing as I feel I’m deep into my LP12, and a Karousel is likely on the horizon. However, if I were not deep into an LP12, or didn’t have an LP12 at all, I might look and listen to a VPI Scout. I heard one  a couple of times, with a Grado cartridge, and I was mighty impressed by what I heard. 

LP12 is the classic bottomless money pit piece of kit to be found in the whole of audio.  

Basically an Ariston RD11 / Thorens TD150 endlessly milked thereafter. Once you're in deep it's damn difficult to cut your losses and get back out - but not impossible. The sheer cost of the upgrades is truly bewildering to anyone outside Linn marketing plc. They've been spewing the same old spiel for decades and decades.

For sure there are numerous high end turntables out there to chose from. I heard the Thorens TD1600 last year and was very impressed by the scale and authority of the sound, plus the impressive low noise floor.

However, it would be remiss not to consider other contenders from the Funk Firm, Rega, Garrard (restored), and particularly the extremely fuss free Technics decks with their astonishing specifications.

Personally I'd get the SL1200 for an end stop and an easy life and consider a future speaker upgrade - but that's a really tricky one which will involve a considerable amount of auditioning.