Not a silly question. Its not the casters themselves but the distance off the floor that makes the difference. There was a post on this board recently that the owner of a BRX410 complained about losing low end and he couldnt figure why. When asked if he raised it off the floor recently he said yes. After putting it back on the floor he said the low end returned. He was happy again. Wish I could find the post.
Having said that just buy this:
http://www.carvinguitars.com/product...p?product=DB35
My BRX210 sounds real bassy right on the floor and loses low end when I raise it. I keep a 1X15 under it.