The JCrew one seems nice for layering purposes indeed. I would sooner wear it underneath a blazer, a cardi or a denim jacket than wear two turtlenecks on top of each other (I haven't seen the catalogue, though, maybe it's a nice alternative?).
'Some warmer options': OK, let's have a look (I'll try to control myself; each time somebody asks for suggestions, I go a little link crazy;-).
http://www.bluefly.com/Inhabit.....detail.fly
http://www2.victoriassecret.co.....rfnbr=5190
http://www.anntaylor.com/catal.....ory=Misses
http://www.tulle4us.com/sweaters/A1174/
On the Esprit website are at least 3 different no wool 'rollneck' sweaters in lovely colours (can't link to them directly)
http://www.espritshop.com/?mc=.....esprit.com
http://shop.nordstrom.com/S/29.....7&P=1
http://shop.nordstrom.com/S/29.....7&P=1
http://www.jjill.com/jjillonli.....ID=K108283
http://www.mangoshop.com/redir.....o=73210709
(Material is not mentioned though)
http://www.forever21.com/produ.....38;Page=14
http://shop.nordstrom.com/S/29.....0423c27407
Love this, very expensive unfortunately
http://www.bluefly.com/Leo---S.....detail.fly
Finally, something with a nice detail!!-)
http://www.bluefly.com/Zooey-p.....detail.fly
http://www.bluefly.com/C---C-C.....detail.fly
http://shop.nordstrom.com/S/29.....0423bb4e95
Grrr, this is rather frustrating! As with basic sweaters (see Patience's thread), I think it's nice to have a turtleneck with some interesting details if you are planning to wear it as your only (or at least top) layer. But this appears to be hard to find when you need something without wool...