I am doing the same thing and after reading various articles right or wrong decided to change the tension strut in additon to the lower control arms and ball joints, this is what i found and ordered.

Ball Joint Febi Ball Joint X5|4.4i Febi Price: $32.95 Qty: 2.00 Part #: W0133-1627472

Control Arm Lemfoerder Control Arm X5|4.4i Lemfoerder Price: $70.95 Qty: 1.00 Part #: W0133-1665396

Control Arm Lemfoerder Control Arm X5|4.4i Lemfoerder Price: $124.95 Qty: 1.00 Part #: W0133-1665394

Control Arm Febi Control Arm X5|4.4i Febi Price: $87.95 Qty: 1.00 Part #: W0133-1614680

Control Arm Febi Control Arm X5|4.4i Febi Price: $82.86 Qty: 1.00 Part #: W0133-1665393

i bought at autopartswarehouse.com after shopping around.