For me, I see only 2 options (well for me anyway) the 370 or a 911 both just seem the perfect natural progression. However, the F type....
The 370, you know what you are going to get servicing and running will be more or less the same as the 350. The 911 more performance than both but a more rounded car overall. The service costs and parts hmmm could be a deal breaker even more so if you get a bad one.
F-Type, much bigger investment but the looks are unrivaled.