BB30A

I share your pain, less than 500kms on my Giant Defy and it has literally creaked/clicked from the 2nd ride. Push fit BBs are the spawn of satan. I am also looking at adding a more robust solution (BBright/BBinfinite...)

All Shimano cranks work with a Praxis and BB30 frameset, that's pretty much the point of a praxis adaptor.

Thing is though, a praxis bb30 adaptor will not work if your synapse is a BB30a bb.

Cannondale will I reckon, keep changing their BB's every few years to try and gang rail you into buying their cranks. They don't want you running shimano chainsets. 

That and the seatpost trick was enough to put me off get a warrantied CAAD12 frame. 

'Sure we'll give you a new frame but it's got no seatpost and you'll have to fork out for one of our cranks, that'll be £300 please'

Nice one.

I can highly recommend something from Wishbone  - they have a BB30A option for all mainstream chainsets. I use their BBRight/Campagnolo UltraTorque model and have zero complaints - and I'm a fussy bugger.

http://www.wishbonetw.com/pro_2.asp?cate=127&id=127

Have you pulled the crankset off to see if you have bearing issues? PF30 bearings do wear out causing a "creak".Remove the cranks, pull a seal from each bearing to clean and re-grease the cartridge bearings. If the bearings feel rough after this service, or of there is play in the bearings, it is a sure sign the bearings are worn out and need to be replaced.

Praxis BB's are sold as Campag or Shimano or SRAM crankset compatible. You decide on the crankset then order the BB accordingly.