Axtl, as Rrog pointed out, all of the ARC tube amps are very good. However, IMHO, the D70 and the D115 are the cream of the crop from that era. ( With slight preference given to the Mk 2 version of each).
If you don't need the extra power, I prefer the D70 to the D115 or the D90. Again, like Rrog said, it depends on your budget.
If you don't need the extra power, I prefer the D70 to the D115 or the D90. Again, like Rrog said, it depends on your budget.