Pass Labs is a great choice, but not in your budget. A old Threshold would be perfect. Something that might not be a conventional recommendation, but was surprising good for the money is the Sunfire amps. They are powerful and high current. At used prices, you can always sell w/o a loss. I've heard them drive plenty of tough loads.
Something else is a BATvk500, in your range more or less. Cheers,
Spencer
Something else is a BATvk500, in your range more or less. Cheers,
Spencer