For that budget I'd look hard at IR Defense too. Armasight is also good as well. I have a 42mm prometheus spotter and it is really a good unit.
Will this be your only thermal? If so you might look at getting a lesser priced scope and a handheld. Its kind of a pain to scan fields with a rifle mounted optic. I have both a handheld and a gun mounted and it works great. I use the handheld the most.
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