Glad you enjoyed your CS and also that you're staying in the Porsche family. Just wanted to throw my 2 cents in here and say that a MODIFIED CS changes the comparison quite a bit and that even with the extra costs of the modifications you most likely come in well under what a 911 C2 costs and also most likely can outperform it due to the inherent balance/nature of the CS. I LOVE BOTH CARS but yes, I own a thoroughly modified CS.
A stock CS is I believe rated at 297 hp at the crank, just by adding in a full aftermarket exhaust/sport intake filter/ECU reprogram you can get up to around 350+ hp at the crank AND greatly improve the sound. My car and many others are there! So that puts you almost exactly on par hp wise with a stock 911 C2S (355hp) and within 30 hp of the 911 C2s with the X51 kit (381 hp) but the CS is a few hundred pounds lighter than a 911 C2S I believe... Straightline they should be very close, in the twisties or on a track the mid-engine nature of the CS should give it an appreciable edge... There are many folks on here that do track their cars on a regular basis and could speak to that better than I.
911 C2S Stock MSRP (US) $83k
CS Stock MSRP (US) $59k
That leaves you around $24k of aftermarket performance enhancements you can add in just to get to the same price of the stock 911C2S... Throw in the X51 kit and the gap gets wider still.
Not trying to slam your choice AT ALL! By all means drive the car that makes you the happiest and everyone understandably has different prefs.
Just playing devils advocate here a bit.
My CS has:
Dealer options
Sport Chrono
Sport Seats
Auto Climate Control
Pref package (Bi-Xenon, rains sens etc...)
19" Carerra Classic wheels
Aftermarket options:
Full Milltek Exhaust
Evo sport intake filter
GIAC ECU tuning
Techart aero kit
lowered coil over Bilsteins
Stiffer sway bars
Avic Z2 touchscreen radio Nav/phone/Ipod (+amps, upgraded speakers)