Why don't you try outputting one of them at 480p? You are doing double scaling that can't help your picture. You would also be better off with the A3 set to 720p. Interlacing things is a sure way to screw things up.
I find I get my best picture from the TVs scaling on my Parent's 768p panasonic plasma. All this scaling talk has everyone all confused. Your TV's scaler HAS to be better than any image scaled twice, and is likely much better than an image scaled, then interlaced to 1080i, then deinterlaced, then scaled again. Does fish taste as good the second time you heat it? No!