I like Darrel's speakers the Hawthorne Duets specifically. I had a good listen to them about 6 months ago.
But the Summas (the only Geddes speaker I've listened to), give you more dynamics and don't lose the OB openness in my honest opinion. It really shocks me that this is possible. Knowing Earl's design prowess I'm sure the Abbey's and Nathan follow suit. However, after reading Earl's theories which are backed up by measurements and having listened to the likes of John K's open baffle Nao II's, Sigfried's Orions and similar designs I feel its Earl's technologically advanced waveguides and Homeless plug that make that difference. Several others who own or have owned open baffle designs comment on this on his website, under 'recommendations.'
There is no substitute for listening to them however. Knowing me, I'll probably own both types of loudspeakers, however the Geddes design has the edge. Never before have I heard concert level performances that sounded so smooth. Most of the Lowther designs I have heard have this 'horn' coloration which is completely non-existent in Earl's designs. I've stopped looking at Lowther based designs since then. However, if you really like the 'Lowther' driver, Dick Olsher does have the BassZilla kit available as an option but it is considerably more expensive than the $1600 budget you have, as the Lowther driver is pretty expensive by itself.
Anand.