MEG - I believe you're on the right track with the pale tone on tone rug. It is the perfect choice to tie in your gorgeous fabrics. Just make sure it's the same color as the background in your floral fabric. (Is it cream or pale grey?)

If you go with a rug in a solid grey or taupe - you'll never be able to match them to your sofa or loveseat.
If you choose a rug with a definite pattern - you'll limit yourself for choices in pillows, drapes and art.
I've posted your fabrics and rug choice below along with a suggestion for a different patterned rug. The reason I chose this particular pattern is because it works better with the playfulness in your floral fabric. It's not as traditional as your rug choice and this more modern look will allow you to bring in some transitional accent pieces which will give you a more interesting space in the end.