I've been using a 2227 for a few months on a 100ltr tank. Mine was second hand & had been used in a marine setup, so I replaced all the seals & boil cleaned the media.
It's located in a small cupboard under the tank & I can't hear it in use
It's really good at what it does, but I have found that without the pre-filter in use, (Eheim say it's only needed for the first 6 - 8 weeks) the water tends to have "bits" floating about as there's no foam or polish filters fitted inside the canister.
I've read the same as you about them not being recommended for CO2 injected planted tanks. I have my CO2 monitored & controlled with a PH controller. I've just used a 2kg fire extinguisher in about 6 weeks on my low'ish (about 1.5 wpg) densely planted tank. I've checked for CO2 leaks etc, none to be found. With the PH meter set to 7, the PH swings between PH 6.90 & 7.1 with the CO2 on/off. Gravel & rocks are neutral. The plants are pearling, & the fish are happy
But, it seems to be using CO2 at a high rate compared to some I've read on this forum. So, having read the same posts as you, I've ordered a 2071, hopefully have it installed & running by next weekend
I'll let you know how I get on & if the CO2 usage goes down any.