Get the "new r-box" from rockminer.
Mine has been hasing with no issues for months.. The U3 seems like a good idea alas is sounds like it zombies a lot :S.
I have S3's and a r-box both are awesome. The R-box is cheap and only uses 100w which is nice.
lol it is only 100 ghash, Get the S3 over that since you can buy them cheap and used, they do decent undervolted.