At the shop I worked at (JL Dealer) until 2011 for 10w3v2/12w3v2 (similar power handling to v3) around 500 watts was always great for sealed.
Going with you are using a 1ft^3 sealed box I have believe we saw a 2-3 ohm max box (impedance) rise.
If it needs to be JL I would say go with:
Good watts are Good Watts, a honest 500 or 1000 @ 2 ohms or whatever watts are going to perform in a similar fashion.
1) JX500/1D (Cheapest) but still 500 watts. Unregulated
2) JX1000/1D 1000 watts, plenty of headroom, amp gain set correctly.) Unregulated
3) XD600/1v2 Nicer Amp looks wise... Unregulated
4) 600/1v3 Slash...Works and looks great...And never saw more amp failures. that JL Slash .....Stiffly Regulated.
5) HD750/1 Slash...Major improvement....early versions had a recall as they caught on fire....I assume they have improved. Stiffly Regulated.