I am DIY fan, and I agree with the notion that DIY doesn't neceserally get you better value but in this case when you have $1500 and want oomph as your priority it won't be too hard to match directivity with compresion driver with a 12/15inch. In saying that, I get DIY is not for everyone.
I also get that for $1500 it will be hard to find a good design based on a compression driver and 15 inch woofer which is what I recommend as per your requirments.
In this case, the JBL HDI might be a great option as it measures well, there is also other JBL that use copression drivers and have measured fairly well within there respective price ranges also take a look at
www.kvalsvoll.com
I also get that for $1500 it will be hard to find a good design based on a compression driver and 15 inch woofer which is what I recommend as per your requirments.
In this case, the JBL HDI might be a great option as it measures well, there is also other JBL that use copression drivers and have measured fairly well within there respective price ranges also take a look at