I have the PPI Phantoms in stock. A 4 channel and a mono would be about $400 together. I can also get you the Massive Audio NX5. The NX5 would give you about 400W to a dual 4 ohm sub. The P1000.1 is rated at 725W @ 2 ohms but it's underrated.
Another option is an i520.4 and an i650.1 from the PPI iON line.