well it 100% depends on what you want from your setup or subs. the type r is a pretty solid mix between power sq and spl. but if your looking for subs that will get you noticed from far away, shake walls, break things in ur car... etc. (basically if you want your system to be extremely loud) then go with the l7's. but if you want your system to push out alot of air, sound incredible, and hit lows almost as good as a 15" sub then id go with the type x.
btw if ur upgrading to the type x (which is what i would get, but thats just my opinion) dont expect a big dB change. in fact alpine purposely built the type r to get louder than the type x. although the type x can handle much more power and make your music sound much more clean