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!
'12 F10 550i (Dinan Stage 5/Intercoolers, CF Intake, Brace, Shockware, H&R Springs, Eisenmann Race Exhaust, CF rear difuser, Giovanni "Lindo" Graphite 20")
'10 e71 X6 35iDrive SAV (Space Gray) - Gone
'06 e85 Z4 M Roadster (Black Metallic) -Gone
'08 e92 M3 coupe (Sparkling Graphite) -Gone