Hi JR.

The difference between the JBL and the Kilomax is a tough choice. Blind test, money no object. JBL will come out on top. Wayne has chosen well to make the JBL driver his top dog in the Pro series. It's an awe sum driver and very well respected, (and envied!)
As far as bang for the buck goes, I would have to toss my hat into the Kilomax ring. It is more bang for the buck. When you get into the 300+ per driver range. Getting what you pay for begins to have diminishing returns. I personally run JBL drivers. I like them. I pay almost retail for them too! I just dont use enough to be a contender in the pricing structure. ( I get TAD at better costing than JBL !) T^he Kilomax is a real tough driver to beat for the money. It sounds clean and deep with punctuality.

I have not used any Eminence Magnum drivers yet. These were made with many similar characteristics to other top low distortion drivers and I understand they sound great. I'm considering them for an upcoming project in fact. Also into the ring are older JBL drivers. I have heard some but with only limited use compared to some of the experts who have been in this circle for many more years than I. I hear tell the 2205 and 2225 have a softer suspension and are actually better for home use than the 2226. If you can find these at a good price I suggest a prompt purchase.

For the 3Pi which uses the 12" Delta LF. I have not used this driver in a 3Pi. I favor this drive very much and have used it quite often in my own designs. I like it better than it's 15" big brother Delta 15. The Omega 15 will outperform the delta 12 in my book and the Kilomax still on the top of the pile. Two delta 12LF or a pair of magnum 12's might be something out of this world.

If you have a budget to stay in. The Kilomax will absolutely not let you down. It's just tremendous. If you can pony up for a JBL, They have the Name, the Performance, the Sound, the Quality and, the, Resale value.

I just want to say one more thing in this long winded..... Get what your comfortable buying. They all sound great. There isn't any point in overextending yourself to reach the next level. Get a kit. Work out a design. Have some fun building a project and save a few bucks doing it. Sit back and relax while you listen to things you never heard in music before. It's all about the speaker....

Bill