What are good external speakers for the T520? Bluetooth?

[Dude]

What are good external speakers for the T520? Hopefully bluetooth. As many of you know I have tried for the past couple of weeks to find a way to increase the speaker volume on my T520. I tried SRS and some other programs, but none of them really boosted the T520 speaker volume to any significant degree. Therefore I think my only option is buy external speakers that would have good sound and be able to increase volume. Enough to fill a average sized room in a house, such as, kitchen or den.

Does anyone have experience with battery powered, bluetooth speakers? That would be my first choice. I have seen some on-line but not sure how they would perform or last. Maybe there are some that can connect to the T520 and charge while they play. What have others done for portable audio play?