Maggies and Subs - REL vs. ACI

Not tried the ACI but had considered it until I found a good deal on a REL to go with my 3.6s. Was very happy with it for two years or so, when it was in a corner. Then I changed to a higher-res CDP and thought the bass was undefined and bloated. Moved the REL out of a corner but kept it near a wall. All is fine again.
The REL may be the one item in my system I have never had issues with and would not sell it because I would simply have to buy another at twice the price.
REL is widely reputed as being THE musical sub to go with Maggies. Maggies need a v. fast sub and the REL supplies that.
Sorry can't help with the ACI but I believe they have a money-back deal. Also Tweeter/Hi-Fi Buys sells REL and their refund policy is good. If not one in your area I think they will ship, but return may be difficult in that case.

Ditto w/Kck. Maggie 3.6's mated to a REL Strata III, against a wall, not in a corner. Excellent. No experience with ACI subs, but very very very happy with the REL/Maggie combo.

You might want to look at the Sunfire Architectural Signature Subs. I have two mated to my 1.6 QR's. They are astounding in sound quality too.

The only sub that I found quick enough to keep up with my Maggies is the Talon Audio Roc

The Force is one heck of a sub, it would make an excellent match with your Mags.

I am a using stereo pair of Sunfire Signature subwoofers with my MG 3.5/R with excellent results. The blend is seamless when the subs are configured and positioned properly (the subs must be kept away from room boundaries for best resutls).