Thanks for the reply and you might be right. I believe I am using the 2v based gain setting (ie most gain).I don't think the wattage is likely to be the issue, as 50 extra wpc would translate into a barely noticeable volume increase. I'd guess it's more likely it's the amp's gain. I assume you've set the Benchmark to the highest gain setting? Even then, through, it's spec'd at (if memory serves) 23dB of gain, which is fine, but a bit lower than the 25-29dB gain that most power amps provide. Compared to a 25dB gain amp the difference might not be noticeable, but compared to a 29dB gain amp the difference might be pretty noticeable and you could conceivably be finding yourself running out of volume range on your source component or preamp. (The Benchmark does provide 29dB if you have two of them and run them in bridged mono mode).
I haven't investigated it enough, since right now I don't have a real preamp and am using a Magni 3 temporarily as a preamp. This means I also have a rca -> xlr adapter cable going into my crossover (venu360). Benchmark makes more obvious provisions for consumer 2v audio than the venu360.