I had a TH500 for a bit , for me it was all snarling mids and really lacked proper oomph down low and any sparkle at the top, I moved it on pretty quickly,
I wondered if it was the cabs I was using but I've since used a TH500 a few times when they.ve been house amps or festival backline and I felt the same, I'd try a different amp mate, last time I was in bassdirect I tried most of the class Ds and for me the Genzler and Mesa Subways were the best, I thought genzler was really versatile and the mesa had an openess and clarity to the tone . I've since got a subway D800 and now I'm really tempted by the WD800
I liked the berg CN but the ceramic bergs are for me the best cabs ever( why did I sell them???) and as good as neo cabs have got they don't quite match up, but like you say weight plays it part
I'd go for option 2 change the amp