I think that before you start picking speakers left and right, you need to ask yourself whether you want speakers for listening to music or for monitoring recordings. Speakers for listening to music will often have some high frequency emphasis with some rolled off bass that colors the sound a bit. Monitors will usually strive to have as flat a response across the frequency spectrum, which is great for monitoring, but may lack the life of speakers that you want for relaxation and music listening.
Speakers like the Adams and the KRKs fall squarely into the monitoring category, while some of the other speakers mentioned here, like the B&Ws and the Silverlines are more for music listening (although they may say that they are in fact miniature monitors, there are better choices for that application).
If you want monitors, then you can get a pair and be ready to plug and go with your Grace unit and an external source. The drawback is that the sound may be too dry and clinical. If you want loudspeakers, then you would need an external amplifier and a pair of speakers, in addition to the source. Their drawback is that they may sound too loose and euphonically colored for your application. Everything is a trade-off within a certain price range.
As for the sub, it depends. I have a set of B&W CDM1SEs as my main speakers, which have served me well through a succession of apartments without a sub. Now that I have a house, I'm strongly considering adding one because the B&Ws only go down to around 65 hz or so. Those bass notes are important, but if space or budget are considerations, you can be very happy without one.