Dude I have a 997 and a 4.4 X5 appropriately modified by as many of the Dinan mods I can get. I have an e92 M3 on order now and my advice is to keep the Cayman and trade the 335i for the M3. Remember the 335i is almost 90% of the e46M3 as far as performance wise so you don't really need both the M3 and the 335i which i guess is why you're asking here in the M3 forum.
Dude keep the Cayman its the track star of them botha nd the new M will no be too shabby either!
Besides you're Cayman looks too good to sell or trade!