Thank you. I'll take your advice and go for the 33. I don't know how my 45 SET amp will do on this 94 dB speaker. I see that the specifications show 8 ohms and I'm imagining that is an average rather than the minimum(?) I've never found a published review of any of the Odeon horns and have not seen any of their impedance curves.If you can swing the 33, go for it.
The mid horn in the 33 does play a lot deeper than the one in the 28/3 what makes the 33 more coherent.
The 33 also goes deeper in the bass region what makes them sound more grown up.
In Addition, they are 1 dB more efficient that the 28/3.
The only "downside" is that the 33 are a little bigger and heavier than the 28/3. But that is not really a problem because the eclosures are modular. I moved the 32 and the 38 several times in regular smallish station wagons (Volvo V60 and BMW 3)
I love the modularity -- we uncrated the 28s and the set-up, including the lifting, was very easy.