For that kind of money, you could conceivably find one of the player-grade Gibson A's from the teens/20's. Like an A or A-1.

I met a guy last summer who got a 20's Gibson Junior A snakehead for about $900 Canadian--under $600 US. -the snakehead style peghead (narrowing to the end) usually adds about 40% to the selling price.

Also, the Martin A-Style and B-style mandos are surprisingly affordable, even vintage ones. They aren't bluegrass instruments but they have nice sustain and sweetness. This Guy has a couple, Elderly.com usually does too.

Find that 8-string!

W-O