Well, I'm not a fan of the l500xl (its not dreadfull, but I'd never go for one), but the painkiller is what I'd point you to in the BK range thats most similar. The PK has a much bigger sound thats not grainy (which the BL is) and its lows are lower and there are more of them, and they are tighter.
I think the BL has a higher resonant frequency, but its overall character of tight cruch is most closely matched by the PK.
I recommend you get a PK, but if you want an l500xl, go for it.
Oh, word of warning: a mate got an l500xl and it screams with microphonics. Never taken any other than that one loud enough to get the same result (never above tv-volume), but my BKs were quiet through the same amp with the same settings in the same place relative to the amp (and closer for that matter).