Hi & welcome! I've not kept any dwarf boas, but I had a BCI for many years, & also raised many rosy boas for years (& still have one). If your heart is set on a dwarf boa,
I don't think a rosy or rubber boa (or sand boa) will fill quite the same spot. From what I've heard about the dwarf boas, they can be more high strung than regular boas,
but you can let a breeder know what you're looking for & in any event, (considering how feisty my BCI was when I first got her) I wouldn't let that stop you...most can be
worked with & calmed down. My BCI changed many hands before she was turned over to me (for biting everyone), but she never bit me even once...she was just terrified
& she learned she was safe with me. (On the other hand, she wasn't what I'd call a "beginner" snake.) If I didn't have more than enough snakes, I'd love to have a dwarf
boa too; I seem to recall they're a bit pricey though, starting at or above your upper price range.
And thanks Richard...I LOVE the longicaudas too.