I notice on the Salk website that there are Ellis 1801TLs and Ellis 1801f models listed. They look similar in the pictures, same drivers?
The prices are different though. Does anyone know the differences between them?
Yes, they are the same drivers, probably the same crossovers, but different cabinets.
If I remember correctly, the first Ellis 1801 design was in a ported bookshelf cabinet. Dave Ellis originally designed it, and he asked Dennis Murphy to "fix" the crossover. Dennis's crossover became a standard feature of the 1801.
The 1801f is in a ported floor standing cabinet, and the 1801-TL is in a mass-loaded transmission line (MLTL) cabinet. If you ask Jim, he'll probably recommend the 1801-TL over the 1801f.
Jim Salk's first speaker, a DIY job he built for himself, was the Veracity HT-1. It was a variation of the 1801. It uses the same woofer with a ribbon tweeter instead of the dome. Jim also ran into crossover problems and asked Dennis to "fix" it. That began their long & successful relationship.
When you asked your original question, you got answers expressing a variety of opinions. Not surprising. Honestly, I think you can't go wrong with any of these three speakers.