I would go for the Lunt all the way. Higher chance of getting good quality etalon. Myself using 60mm single stacked - bought used for £2100 end of last year. With good viewing and right pixel sized cameras you can squeeze from it a lot. The closeup was recorder with 178MM and cheep 2x Barlow so quite oversampled, and full disc ( just a surface ) without Barlow and the same camera ( lots of detail for SS )
I am considering double stack but not now - this is the worst time to buy due to eclipse in US next month. I think after April, there will be a lot of people selling used equipment purchased just for this event.