You might also consider looking at the Focusrite VRM (Virtual Reference Monitor), which can simulate a number of monitors. I appears as out of stock my most retailer (not sure why, I've emailed Sweetwater to find out), but I see that it's still available at the Best Buy website for half price.
Edit: Sweetwater verified Focusrite VRM is discontinued.
I've got it, and it makes it easy to "try out" the mix on a wide variety of speaker systems. Sadly "car" isn't one of them.
In particular, it lets me see how
badly a mix that sounds good on one set of speakers may sound on another set.