I'd go with a SRI as it will increase your MPG.
As far as the stress bar, it's a waste of money. Doesn't improve the stiffness of your focus around corners. The RSB on the other hand, will make a difference.
2013 Ford Focus BOOS[ST]ED
2010 Ford Focus "S"edan (11 Psi, GT28RS) - Sold
ROTM Nov '11 (2010 Focus S)