Benchark dac1 output as pre high enough?

The gain on the unbalanced outputs is low (if you're using the balanced outs, the gain can be adjusted). But if you're not running out of range on the volume pot, I can't see that it's a problem.

Yes, the Benchmark has more than sufficient output to directly drive any amp, either with the balanced or RCA outputs. It's specifically designed to be used as a preamp - because it is in fact a preamp - and IIRC the manual recommends using it that way, to drive an amp directly.

I presently use it to directly drive a Pass Labs X150.5, a medium sensitivity amp, and have also used it to drive Classe and Hafler amps, and the volume control has never past the 9 to 12:00 position. You can check the manual online for output specifications - Benchmark gives copious information.

I have a Benchmark DAC1-Pre that I am using with 2 Krell FPB350 MCX monoblocks. The combination works fine at the regular DAC preamp output setting which uses a factory 20dB pad setting. The idea is to achieve normal listening levels with a volume control set above the 11 o'clock position. If you need more juice, there is a 10 dB and 0 dB pad settings.

Hope this helps