I have four Mach 5 Audio X-Mass 18". I bought them two years ago with the intention of doing an IB installation in my attic, but never did the install. At this point, I have decided my Maelstrom 18" with 2 PR's and EP2500 is enough bass for my room.
The WinISD driver file is attached. 4 of these will perform very similarly to 2 of the FI IB318's with much less power and less cone movement. I bought the 4 in a special Christmas (hence the name X-Mass 18...) promotion for $453.27 including shipping. I was going to run them off a 350 watt x 2 Carver amplifier.
I'll sell for $225 + shipping. Get 4 18" drivers for the price of one IB318! Worst case, you hate them, rip them out, buy four IB318's, and use the same manifold. Any way you look at it, it is is an inexpensive way to try out IB. That was my logic when buying them, but now I don't have the desire to build an IB install.
I didn't PM you because I thought maybe the forum could comment on these drivers if anyone has used them. I haven't used them, so I can't tell you how they sound.
It is the file extension for a driver, not a project. Start a new project. When you get to driver selection, select "New". Then load the file. Set it up as a sealed enclosure with a large (100 ft^3 or so) volume.
Alternatively, I have also attached a driver file (.wpr) for a single driver in 100 ft^3 box. Change driver count to 4 and box volume to 400 ft^3 to see four drivers.