Good in what?
Confirmation or bloodlines?
Boones Little Buckaroo is a very predominant in whos who in mini horse world and well known and beloved to some breeders that they would linebreed or get ancestors with every line that goes back to Buckaroo.
I have seen Buckaroo as an elderly horse before he was sold to a family in Indiana while Mr Boone had to have some money for his heart surgery. Seen his son, Buckaroo Two, as a youngster and looks really nice.
With the lines going on right now, Stouts lines are ok but good in broodmares. Would not sell for high prices in todays market. Rowdy and NFC horses and have not kept up to date on popular bloodlines. However some folks to try to maintain the old lines and keep it that way without getting into the "fad" bloodlines of today and gone tomorrow.
I can not advise you what bloodlines would be popular right now but maybe some hindsight which lines work well with Stout lines. Any of the NFC line horses would be good choices as well as Egyptian King lines works really well and got champion lines for a couple of generations. Hemlock Brooks, Dell Tera, Johnston, Rowdy often works well with Stout lines too.