Best upgrade path for an older but nicely maintained Linn LP12

I dropped off my 1978 LP12 for a tuneup yesterday. To do this I must make the nearly four hour round trip to Accent on Music in MT Kisco, NY. I live in Guilford, CT and although  a long drive, David Wilson is the only person I have ever let work on my LP12. It was last tuned up in 2012 so it's time. While there yesterday David plugged it in for a quick listen and I was relieved to hear that it was still "a very nice sounding LP12". I knew that already but hearing it from David is very reassuring. My table is currently set-up with a Lingo 2, Ittok, and Dynavector 20x HO. My system consists of a McIntosh MAC7200 and two Pranafidelity Bhanas on Sound Anchor stands.  I was glad to hear the folks at Accent agree that the Dynavector seems to show no sign yet of wear. I've owned that cartridge for 7 years but only play it for a few hours a week and not every week. We of course discussed a few upgrade options and that is why I am asking the following of this group.

How much of a listening difference will an upgraded keel make? It will cost $1200 but I am told it will make a big improvement. Not that I doubt what anyone at Accent on Music tells me but your opinions are valued too. Thank you all in advance for your thoughts.