I think it's rated at 60 wpc into 8 ohms. Input impedance is 20K ohms, which is not particularly flexible. But if you have sources less than 600 ohms output Z, then I think you're likely okay with a bit of room to spare.
Having said that, note that the preamp section is no more than a volume pot. All gain is in the amplifier section. So if you have a source which is known to not work well with passives, the LFD may not be a good choice.
It will take awhile to open up. In Sam Tellig's review of the MKIV, he says 1 week. I think it's more like 3 weeks -- but I wasn't playing music all day long, and Sam may very well have been exercising it more.
My system right now is:
Zu Soul Superfly
LFD LE MKIV integrated amplifier
Eastern Electric DAC Plus, with LM49990 opamps
2011 Mac Mini
Audirvana Plus music player with iTunes integration
The EE DAC with the LM49990 opamps is a bit edgy unless you use a great player like the Audirvana Plus, which comes with SRC and dithering by Izotope. You can set up minimum phase, apodizing filters etc. which gives you a smooth top end with no fatigue.
I am surprised that the little EE DAC is as good as it is, but it is only true when I'm using Audirvana. I suspect it would also be good with Fidelia and Amarra, but PureMusic would not be a good match. I have heard / owned all of these players, and I find PureMusic is better for systems that are a bit veiled, where Audirvana, Amarra and Fidelia are better for systems that may be too lit up. In this case, the Sabre DAC chip is certainly on the brighter side of things.