Radeon HD 4800 series -- it's a lower spec chip, but it has essentially the exact same feature set. The $80 HD 4670 has 512MB of GDDR3 RAM, while the $60 HD 4650 uses 512MB of GDDR2 memory; both are relatively power-sipping with 60 watt and 50 watt draws respectively under full load. Should be out soon -- HotHardware just tested an HD 4670 and found it to be quite a performer, check it all out at the read links.
Read - ATI Radeon HD 4600 series PR
Read - HotHardware test