i was similarly afraid of owning more than 1 car when I got my 8 :
Then I got the SL, with the idea that I might sell the 8.......but i ended up liking having both, different cars for different driving/weather
Then I realised I needed something for drive the family around in so I got this........
A car for every occasion - in short - if you have the storage/garage space, keep both, there are literally tens of thousands of Porsches out there, you'll always be able to find one but finding another E31 - a "CSI" too? much harder...