VNC Again!

Hello,
I am using proxmox and a kvm machine via the java vnc console you provide.
It is very slow, expecially on slow connection because your vnc is configured to not compress (e.g.: jpeg) data.
I have tried to use an external vnc reading forums and tutorials but the best I was able to reach is a:

No valid VeNCrypt sub-type

using linux tigervnc that is the ONLY viewer supported.

Please do not tell me "simply install a vnc/rdp/nx server in your virtual machine and use it".
You forgot a very important thing: the vnc provided by proxmox let me see the CONSOLE (bios messages and so on) of my vm and the boot sequence!

So please tell me how to use an external viewer or how to make the java viewer faster.

Thanks,
Mario