Any of the Asiatam / Taigen metal lowers turn a clunky plastic toy into a scale-driving model almost instantly. The difference is night and day and totally worth it.

Rctank.de currently offers the only HL-compatible Panther metal hull, and I believe they also have had the Torro Tiger II for quite some time as well.

I have the metal Tiger, KV, and Panzer 3 hulls & they are excellent.