Peter,
Hmmm
I can't find any SME-90 filters in the US - In the UK they are shown as 2720bgp ($5400) - to get a DS double this cost!! Plus say a BF15 at us699 ($1000) Brings it in at around $11,800
http://www.meadeuk.com/Coronado-Etalon-Units.html
For the Lunt there's only 50mm,60mm and 100mm external DS etalons ( the others are internal)
https://luntsolarsystems.com/product...solar-filters/
The LS100FHa is us$5498, then the B1200 (us648) or the B1800 (us$998) either way to get a DS external 100mm Lunt system it's well over S16,600)
Plus the GST, shipping etc etc etc.