The lower radiator hose should always be cooler than the upper hose. But if the delta T is more that 20 degrees, then the thermostat is closed or the radiator is clogged. Since you've replaced the thermostat, it's a good bet that your radiator is clogged. You can try another flush (I hope with citric acid, not hydrochloric), if that doesn't do it you'll have to replace the radiator.

One more thought. There could be debris trapped between the a/c condenser and the radiator.