What driver combination??!!

[saggybob]

So I'm looking at making a portable speaker set up to fit into a specific spot on a sort of mobile trolley setup I've got going, to run of a 12V power supply and to be mainly used as background music.
I'm looking at using one of the 41hz amps (amp6 or amp11 LV) and am trying to decide on drivers, (kind of lacking variety in australia).

So for the questions....the max dimension i have to work with are 45w x 35h x18d in cms (17.5 x 13.7 x 7 inches) and my first hurdle is wether i go for a mono setup with a large 8" or 10" woofer + tweeter or a stereo setup with 2x 6" drivers and 2x tweeters. is there any particular downside to a mono setup, apart from it being mono of course?

also a friend suggested to me that i use 4x 4" or 5" fullrange drivers instead, as within the budget i have this could be more efficient for the money, does anyone have an opinion on this?

I'm just starting out but i'd greatly appreciate the help!