I think realistically this will not be a budget product. You will need to have a more robust power supply, big heatsink, etc.. My guess is once such product hits the market with >$400 online price, there will not be many buyers. I for one don't like to put so many eggs in one basket.
They do make some 5-ch amps with 1ohm stable sub channel, but not with 1000watt output. MB Quart ONX4.80/500 is one. However, having witnessed my quart ref4.80 run stupid hot, I don't know if I would want a comparable amp share a heatsink with a mono amp running at 1ohm. Another is Polk D5000.5 (this clearly was not designed for high output 1ohm operation as the rating at 1ohm is barely above the 2ohm power rating).