For powerful strobes, your choice is basically between Inon Z-330 and Sea & Sea YS-D2. Z-330 is slightly more powerful and has a better beam spread (although due to the T-shaped arrangement of its primary bulbs, it produces a cross pattern rather than an even circle; a diffuser solves this but absorbs some light) but last I heard, it's still mostly back-ordered. If you want to save some money, previous-gen Z-240 and YS-D1 are frequently available used at a discount. If you're willing to wait, the new Retra strobes are slated to be released around May-June, although if past performance is any indication, this is bound to slip some, and then it will take them some time to ship all the pre-orders.