There is one question I don't understand: Threshold T-2 was designed specifically for T-series amplifiers, and the specification for this preamplifier says that the impedance at the balanced output is 150 ohms. It turns out that the engineers have made two devices incompatible with each other? It doesn't look right…Although the general 'rule of thumb' is that it is better to have a low impedance at the output of the preamp and to have a high impedance at the input of the power amp and we should using a minimum ratio of >1:10.
But it is fair to point out there's exception IF THE PREAMP CAPABLE OF PROVIDE THE REQUIRED CURRENT into a low input impedance power amp. For example: krell cast connection, darTZeel 50 ohms BNC and jeff rowland 600 ohms input impedance.