You should be able to use banana plugs with our speakers just fine! Speakers like our A5+s and A2+s use full size 5-way binding post, and are compatible with standard single and dual banana plugs. Most standard banana plugs should be around 4mm in diameter.With the smaller posts, like on the original A2s and A5s, we typically suggest going with pin terminals or spade lugs. The spade lugs will need to have a minimum inside opening of 6mm. You can use mini-banana plugs but they are pretty hard to find these days. The maximum outside diameter you can have on these plugs is 3.05mm, with a spacing of 3/4" from center to center.
Keep in mind that the HD6 and HD3 come with speaker wire that already features banana plugs.