abracadabra:
Moving from a 160hp aircraft to over 200 will make a huge difference in your cockpit workload due to the extra speed and power, and probably not something you need being such a young pilot.
I dunno, I'm in the Seneca 200T these days,and I'm 17. It certainly is fun having 2 200hp engines on either side of you...much more security. Should one engine fail, the other one takes you to the crash site.
15 is a good age to start, but you can't solo till you've passed medical and your 16....go get a medical before it's too late.
jet_breeze, go for it if you think it's right. You obviously sound as if you have the money!