Thanks, everyone. I looked at the Moda marbles online and they look wonderful, but really need to see them in person. I will look for them in the quilt shops locally. Meanwhile, I decided for this first quilt to go with Kona muslin in natural since I know this is a really nice muslin. Took advantage of Hancock's in Paducah's sale (I think today is the last day for it). Because I ordered quite a few yards, it was only $3.60 per yard ($1.80 per half yard) PLUS I got 20% off with the coupon code that is good through today (20MCTU12). Can't beat that price for premium muslin! Have to admit I clicked through the web sales for batiks and added a few of those to the cart too.
This is a quilt I will probably make more than once, so I'm thinking muslin makes a good first run. Next one will probably be a Moda marble if I can find the right color. Thanks again!