personally, i would rather have the big monitors and no sub.
the only potentially major drawbacks i can think of for what you propose are:
-placement. a lot harder to get placement right with a sub-sat system than with a stereo set, especially if your space doesnt cooperate (both aesthetically and acoustically).
-adjustment. without an SPL meter and some calibrating, you are just pissing in the wind for setup. "sounds good" is many times not the same thing as "as flat as possible".
i fought with a sub for a long time, and ended up ditching it. though the pleasure of that big bass isnt there for monitoring anymore, i did find that my mixes were often more easily translated to a typical listening environment (notably those without subs, like a factory car system), especially as i learned what my monitors low frequency cutoff sounded like, and what info below this point sounded like without the sub.
that said, the KRK stuff is nice. i was within moments of purchasing some V8's a few years ago, but couldnt substantiate the cabbage without using credit. they sure did sound nice, though.
a