The Engl Savage certainly doesn't need an attenuator. The 6550 power section is very "clean" - by that I mean it gives a very consistent sound at any volume (as well as the legendary Ampeg SVT bass head, 6550 valves are also used in high-end hifi amps).
In the case of the HK Triamp you might want to try it with an attenuator. In my experience, EL34 valves need to "cook" a little more to get the best sound - in other words, they need to actually be driven in order to sound driven (if that makes sense! :)) Having said that, when I tried the Triamp at LGS '07, the HK booth were on a "final warning" for excessive volume so the amp was turned quite low but it still sounded really good.
I guess having two cabs is going to be cheaper than two decent amps (at least one of which will have to include a cab anyway!). We had a recent thread on this board about 212 v 412, so have a look over the last few weeks' threads....
FWIW, I find that switching my 4x12" to stereo & using just one "side" is as good as a 2x12". I also find that despite its size & >50kg weight, I can carry my 4x12" up/down stairs perfectly easily & it fits in the back of my Honda Civic (albeit tightly). OK, I'm no 7 stone weakling, but nor am I a great strapping super athlete either :( IMHO any averagely built adult male should be able to lug a 4x12 around without too much trouble...
