I had a HLA-300V working with the SunSDR. I sold it as i noticed cutoff's in SSB (CW/Dig was ok as yours). I then used a KXPA100 from Elecraft - it worked fine. Sadly i sold it (too much wires) and then bought a MX-P50 PA from China... Crap - stopped working after 3 months and because there is no real schematics of the board or a support from the seller or factory, i could throw it away soon... never got it repaired after that... At the moment i don't have a driver PA for my SunSdr, so i mostly use my K3... i really miss the sdr, but have no money to buy a complete new pa. The RM Italy PAs are ok, but worse, really worse for ssb...