Yes I have some DCX 464's ... I have tried them in a slightly different box and horn. Impressions so far - better than the BMS4594 and as good as the 4594HE but different.. The 464 seems to have very clear mids and possibly more output capability, but I like the VHF better on the 4594HE. FWIW I think the wave front exit angles and SPL across the throat of the 464 are better than the 4594 so you get slight better coverage from your horn ... just a guess at the moment.
Not sure, still work in progress... but getting the 464 to sound the best you need to address the mid range driver peak at about 5.3 KHz, even though its out of band and cross it over around the 3 - 3.2Khz as recommended by B&C.
...and yes it will work well the 12NDL76 .... just need to check it will fit in the box with the 60 degree horn ...planning to check this all out soon when I have some spare time.