As Cortes said, there aren't really any alternatives to Stax amps that are tempting.
My subjective opinion is that going from the 252s to the 006t and 727II makes for a better sounding experience, but that could be other factors at play than objective sound differences. When plugging the SR-007 into the 252s and swapping it to the 727II, the difference was so staggering that there really wasn't any doubt in my mind. I did the same with the L300 but can't say I remember hearing any significant improvement. When I sold off the 252s and 727II and got the 006t, I felt very strongly that the L500 sounded better on the 006t, however. But again, this is just my completely subjective perception.
Thanks, until someone measures these units, this is good guidance. If I was in the US, I would gladly ship my 252S to Amir for measurement.