If you can possibly swing it, my suggestion is to go to an audio show and get a sense of what is available. It's great fun and you will come away with a much better idea of which direction you want to head. It looks like your amp will handle difficult loads so you have a lot of flexibility of what speakers you can use. It might be time to go with a pair of conventional box speakers.
BTW, I sometimes hear graininess on my Thiel CS6's (Krell KRC-2 & KSA 300S) and I have done the same thing by checking with headphones. It's always in the recording. The sax sound you describe may be the instrument being portrayed accurately. A trailing sax note does sound grainy by nature due to the reed vibrations becoming more noticeable at lower volumes.
BTW #2, I also have a Tubadour IV. Great DAC.