I'd like to get some smartwool to keep warm AND keep dry for 20-35F riding - but am confounded by the options/versions. Any suggestions?

Personally, I would recommend DeFeet Woolie Boolie socks. They are designed for cycling and very warm and durable.

I'll second the woolie boolies, but I also recommend some shoe covers if it's really cold out.

I have three pairs of the Smartwool crew sock in medium weight and they work great for cycling in the winter. I got medium weight because I thought they would be warmer then the light weight but not make my shoes fit too tight. I think I bought my first two pairs at Dick's and the third I recently bought on line because I knew what I wanted.

Medium weight, and make sure your shoes aren't too tight! I ride with medium weight and vented running sneakers down to about 15F and my toes are fine after 30 minutes. Loosening the laces was key. Below that, I switch to hiking boots.

I'm not sure if my Smartwool socks are medium or heavy weight. I help them a bit when the temp drops below 30F, either with shoe covers or with a plastic grocery bag liner. I cut the bag in half vertically, snip off the handles, and wrap what's left over my socks before putting shoes on. That keeps the wind from blowing through shoes + socks. Below 20F it's time for the shoe covers.

I have some Smartwool medium weight socks, but I think that the Woolpower socks that Rviendell carries are much better.

Midwest Mountaineering staff recommended the Fits Sock like this one:
FITS Performance Trail

It's supposed to be shaped and reinforced so you don't wear holes in contact areas.

I have some woolie boolies and smartwool.

I prefer these: SmartWool Outdoor Sport Light Socks (For Men and Women) although they're both very good.

I buy them when they're on sale.

I like the made in Vermont Darn Tough merino wool socks. Below forties my toes get a bit too cold with mesh cycling shoe though so I use them with a waterproof winter non cycling boot.

Smartwool medium weight phd cycling socks with shoe covers. I also want a pair of Pearlys

Thanks all! Got some mid hiking crew and they seem marvelous. Also got a pair of running/athletic smartwool as a preset - very light - only use that in fall/spring me thinks.

Defeet wool blaze or some variety of Darn Tough would be my recommendation.

I've never been too impressed with SmartWool. With the exception of one pair of ski socks, it hasn't held up.

Yup. I second that. They're comfortable. but I haven't had a pair of Smart Wool make it one winter before holes start to form in the toes.