IMHO, the big name brand units are good and worth the price premium. I am using Morningstar (TS-MMPT-45) and am very happy.
Given your question, it sounds like you may be interested in either an actual battery bank monitor (not just voltage, which tells you nothing). For this, the Bogart Trimetric RV-2030 is very good. Or, maybe, just the solar panel output information in which case a remote panel for your charge controller (it is the TS-RM-2 for the Morningstar MPPT controllers).