How loud do you need to be?
In general, it is best to have two cabs with the same layout. I suggest 2 210 8 ohm cabs to go with your LH500, for maximum flexibility. Bring one to rehearsal or low volume gigs, both when you need to stretch out.
If you consistently need to be loud

, you can get a 4 or 8 ohm 410 cab and be done with it.
I had a LH500, and had really good luck with two Bag End S15 cabs, two Aguilar DB112 cabs, and an Acme B2 cab. It goes well with pretty much anything.