For thicker wool, you want a spindle that is at least 1.5 ounces, on up to 2 ounces or possibly even a little over 2 ounces. Since you put the kit together yourself, you can pick to make it top or bottom whorl as you prefer.
If you would like a nicely turned spindle, the least expensive of those is the Cascade Little Si (http://www.thebellwether.com/cascade.html) or the Kundert solid wood whorl (http://www.thebellwether.com/kunspin.html), both top whorl spindles.
Again, you'd want to check the weight is 1.5 ounces or more; the Little Si ranges from 1.0 to 1.5 ounces, the Kunderts from about 1.1 to about 1.6 ounces in solid wood whorls.
The all-around best spinning spindles are the Tabacheks and the Bosworths; they cost more, but they are the type of spindle that you will return to over and over, as a really wonderful spinner.
To have a thicker yarn, you would want a Tabachek Deluxe or Plying spindle (http://www.thebellwether.com/tatosp.html), as those sizes are usually over 1.5 ounces.
Bosworth Spindles (http://www.thebellwether.com/bosworth.html) also come in a variety of sizes; the Midi or the Large both can run to over 1.5 ounces (over 42 grams).
If your interest runs to a bottom whorl spindle, the all-around best one I've run across is the Jenkins Turkish (http://www.thebellwether.com/jetusp.html). They tend to run fairly heavy, so they are great for thicker spinning.
And I also have one remaining Halla Spindle (http://www.thebellwether.com/hallaspindles.html) that is a bottom whorl. Hers are polymer clay, molded and hand-painted, and are lovely spinners. They weigh in at about 1.5 ounces, making them good beginner spindles and also good spinning for thicker wool.
(reply to an email inquiry by me this day)
