Loro Piana, Cucinelli and Piacenza are my favorites for cashmere. I also have a Les Copains cashmere sweater which easily rivals these brands. J Crew and Pringle are my go-to brands for merino sweaters
I can get a reasonable deal on Pringle cashmere sweaters, so have a few of those - they're pretty good - soft, warm and they don't pill. Not the finest cashmere in the world, but certainly good and not too expensive either.
Loro Piana cashmere is very lush and I like it but carries a hefty price tag, even at discount. Good though. Ballantyne are very cool too.
My thoughts on the current Ballantyne sweaters are mixed. Ballantyne once was perhaps the best of the Scottish cashmere houses, but I am suspicious of some of the new stuff.
Hawick Cashmere is still making excellent cashmere sweaters -- including some of those at Knize and Ben Silver. I had a Pringle scarf about ten years ago which was excellent, rather better than the Johnstons scarf I replaced it with.
I have never seen Peter Scott knitwear in person.
William Lockie also appears to be doing respectable work.
I don't know how good they are but I saw some nice silk/cashmere blend sweaters in Banana Republic for around $70 I think. Good color selection.
I also have two of these (they cleared them out for $15 at the end of the season). Nice cut, great colors, shed (pill is the word?) like it's going out of style. I'd never owned a silk/cash sweater before, and I really like these.
Aran sweater are my favourite. I have one being made as we speak from wool that was milled in New Lanark using traditional methods. The wool has flecks of silk throughout. I am lucky as my grandmother is a tailor, retired now, so I am able to just by the materials and she makes them for me.
I just bought a couple Shetland sweater vests from Shetland Collection. They seem to be the perfect accompaniment for Shetland jackets. Hand knit in the Shetland Islands for a very reasonable price. They're at the other end of the knitwear spectrum from cashmere though.