According to Keele (hardly undisputed), the predicted roll-off point in going to be 2*Fs/Qts, which for the Peerless driver is very low, like 130 Hz. According to Fitzmaurice, it'll be good for another octave, but that puts it only up to something on the order of 300 Hz, still way too low.Check out something like the 3820 - http://www.phlaudio.com/main.html
I would advise to to forget reaching up to 1500 Hz in a horn loaded two-way: it ain't going to happen from what I see. Your best bet is to go no higher than 400 or 500 Hz. BMS drivers an get you there pretty cheap: http://www.woodhorn.com/BMS/bms_compressiondrivers.htm