can I drive Firstwatt amps directly from the source?

I'm wanting to experiment with the Firstwatt line of amps.  I'm a transparency/detail junkie and have loved the sound of my SET using 805/300B tubes and have been mostly pleased using gainclones/chipamps and want to move on to these Nelson Pass amps.  I see that their gain is on the low side.  I'm not sure exactly what that will mean for me.  I will want to go directly from the source into the amp(s) sans preamp.  I like the purity I hear running this way.  I've used a Theta Miles, Consonance Droplet 5.0, and Raysonic 228 with the results I want and should be getting a DAC like the Auralic Vega soon.  I will also be acquiring some Tektons for this purpose, possibly Perfect SETs or Double Impact SE.  Will this combo play at higher volumes or will the lower gain on the Firstwatts necessitate an active preamp, in which case I'll likely abort the endeavor.   Thanks for the input!