same performance for 08 and 09 models. It's the same car. 2010 model got the iDrive facelift with 10" Nav screen in HD.
If you are concerned about power it is easy to add over 100 hp for under $500 and less than an hour's work.
Audio: Jehnert Flatline speakers, Mobridge M1000 DA2 prepro, Helix P-DSP, Zapco Z-150.6 amp, CIC iDrive upgrade
Performance: MHD Pro Tune, AR Downpipes, ER FMIC/CP, DCI, RB turbos and inlets, KW V2 coilovers, Fuel-It Stage 2 pump w Ported fuel rail, Mfactory LSD