I've just bought a QSC plx1602 for use with a Hellborg preamp and they are good value (especially used... actually may 'have' to be used as I think they are discontinued). Nice weight and the amp will go down to 2 ohms on each side, though I have no idea when you'd need to do that and I do find it annoying that it is advertised as a 1600w power amp when that is it into 2 ohms each side (500w each 4 ohm side is still plenty enough). Clip limiters, bridging and parallel mode are all useful (the bridging less so IMHO) and it is nice and quiet in operation (nice quiet power down/up as well).
It has low pass filters and they don't make any discernible effect on what you hear from your bass cabs but they do stop your amp wasting power reproducing frequencies that you don't require/perceive.
In summary, worth looking for.