I assume you're using the Hi bulb...
XM-L at rated spec (3A) will be slightly dimmer, but you can overdrive it to match or exceed with good heatsinking.
SST-50 at spec (5A) is basically equal to ROP-hi, but a direct-drive with 4 D cells would go well past -- lots of heat to deal with though.
SST-90 is the only one that will really be a big improvement at spec (9A), but again, lots of heat.