If you want something to replace 600w of HID then you want to get around 600w of LEDs. Theyre a better spectrum than hps/mh but still, 300w of LED does not equal 600w of hps. So as far as finding one to replace it for 2-300 isnt likely.
I can recommend growevolution.com but they dont, and no other LED company, have anything close to a 600w for that price. Even the least powerful model is in the high end of your price range. You can try buying direct from china but they can be very faulty and probably not have a 5 year warranty like most places.
You can DIY and make yourself a multichip/cob LED light out of a few hundred dollars of ebay shit if youve got the tech knowledge to wire it. Its pretty simple but can be confusing.