Here is how 8/6/4 ohm "present themselves" to an amp...
8 ohm is a Toyota Corolla.
6 ohm is a Ford F250 Diesel.
4 ohm is a diesel/electric powered ocean liner(you know...Carnival cruise lines)
(yes that is a bit of an exaggeration...but hey...)
The answer to your question is..."more than likely"...however...
If you haven't had that 3311 very long I recommend(especially since you like it loud) returning/exchanging that for a pre-pro. An Integra DHC 40.2 is around the same price as your 3311. If you plan on getting an amp for the front channel already...you can find a 3 channel amp for the other 3 very easily on Audiogon/Ebay.
Matter of fact...if you don't need 3D ability...
Integra DTC 9.8/9.9 can be had for as little as $700 (you can peruse the various Integra pre-pro forums).
Marantz made some very well thought of pre-pro as well, but they tend to be more expensive(they were more expensive when new, didn't sell overly well when new...and they don't show up for sale very often)
That is my suggestion...but you can certainly try an amp first...then see if the 3311 can handle 3 4ohm speakers.
Just a suggestion...http://www.audiogon.com/cgi-bin/cls....Excellent-condhttp://www.audiogon.com/cgi-bin/cls....-channel-power
That combination, if you can live without ARC and 3D(which both have workarounds anyway), is $1250 and would completely walk all over the 3311, kick it to the curb, bite it, spit it out and ask it to get up, so it could beat on it some more, till the Denon could take no more.