Keep in mind that we dont' know his preferred SPL and distance for listening. With that amp, running the 880s, i actually wouldn't expect alot of oomph at higher SPL.
The $770 USD amp (
https://outlawaudio.com/shop/products/50-model-5000x-5-channel-amplifier.html) only has 120W/ch @ 8ohm and it maxes out at 180W /ch @ 4ohm load (all 5 driven; no where close to a power doubling which gives you some indication of the power supply quality) and has a whopping [sarcasm] 6800uF /ch capacitance (added together 34,000uF which is stupidly low overhead for dynamic peaks.
A comparable used Anthem MCA5 (circa 1999; approx. $1000 Cdn;
https://www.canuckaudiomart.com/details/649777485-anthem-mca-5/) puts out 200W/ch @ 8ohm (350W@ 4 ohm) and has 100,000 uF total capacitance, 20,000 per channel (http://www.soundstagenetwork.com/video/revequip/anthem_mca5.htm;
https://hometheaterhifi.com/volume_6_4/anthem-mca-5-amplifier.html) compared to Outlaw. Brand new the Outlaw is cheaper, but you can see why. Buying an older but used amp gets you ALOT more for your money. Note that there are several revisions of this Anthem lineup over the years and you can get newer units for not much more in used costs with similar specs.
Outlaw like Emotiva is another inexpensive brand and for what they do, they can do it 'just fine', but trying to power LFR880s to some high SPL or in a larger room or a 'distant' listening location, it doesn't have sufficient juice.
My advice, don't turn up any volume knob past 80-85% or you chance some kind of clipping, distortion, maxing out of speakers or amps (if you buy well, your equip will have protection shut downs, but speakers clipping do not shut themselves off). If you can't get enough dB of sound at that point, start looking at your system components and listening environment to determine what you really need to get the sound level you want. Don't try pushing the gear closer to 100% or risk damage.
I will say it again though, everything has its limits. If you wanted to get 100dB at 20 feet away (for example), you need to open the pocket book, get really large (or many) speaker units, or else face the fact that such a scenario is not possible with LFR880s and this Outlaw amp.
