A:
It seems like you have 3 questions here:
1) Would the subwoofer wireless kit work for your BA 2.1 system?
2) What product would work?
3) Would RF-WHTIB work?
Answers:
1) If the subwoofer is self-powered (has a power cord that plugs into the wall) I'd say it would work. If there's latency (signal delay) as reported by many reviewers, I believe your system can't be adjusted and you'd have to decide to live with the delay or return the product.
2) This is a good product, but there are others just like it, although this is a simple connection, so I doubt the results would be different.
3) No. This is a surround speaker system (supports small, weak speakers) so it wouldn't have enough power to drive your subwoofer. I have one of these and it works very well for the rear speakers.