Loudspeakers with a wide sweet spot

A used pair of Avalon Acoustic Eidolons would fit the bill. Best off-axis response of any speaker I've heard.
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Any OHM Walsh speaker (largely omnidirectional).

Also Gallo Ref. 3s.

Blue Circle Pennies also. These are designed to go closer to walls.

Also some Dueval, Morrisons and a few other lower priced omnis.

Agree with the omni suggestion, planars and Alon/Nola a couple more choices.

Audiokinesis speakers offer a wide sweet spot if you have enough space to set them up in your room and use the recommemded 45 degree toe-in so the signas cross about 2' in front of of the listening position. Both the Jazz Modules and Dream Makers are in your budget.