JL /series amps make rated power into any load between 1.5 and 4 ohms. In other words, it won't make a difference which ones you get - two 4 ohm subs = 2 ohm load, 2 2 ohm subs = 4 ohm load, and the 1000/1 makes within 5% of rated power into either impedance, the extra 50 or so watts at 2 ohms isn't enough to matter.
Short version - If you're using the JL Audio 250/1, 500/1, or 1000/1 it doesn't matter which L7's you get, just make sure both subs are the same.
