I have 1000 sq ft, 2 ton pump backed up by oversized XV80. The HP does super, I keep it 68 in the summer and with Comfort R turned on, humidity runs in the lower 50s. Haven't rigged up dehum on demand, haven't felt I needed it. Probably would if I kept it warmer. Manual J was 1.5 tons but since I like it so cold, I wanted to stay 2. This place has R38 ceiling, R13 walls, very tight windows.
I'd say seal the sucker up and put in a small unit. 1.5 ton XR on VS air handler wouldn't be bad. I don't care for the XB units. From what I've read about the reliability of the 19i, I wouldn't touch it and would go the 16i for high end.