Does the amp have to be a tube unit? If not, and you will consider a solid state amp (both new and used), then these 4 amps are in your general budget range and offer excellent performance:
1. Bryston 4B-SST
2. Marsh A400S
3. Rotel RB-1090
4. McCormack Audio DNA-225
1. Bryston 4B-SST
2. Marsh A400S
3. Rotel RB-1090
4. McCormack Audio DNA-225