I think you will be happy with your decision. There is (to me at least) a marked difference between the older V8 and the new twin turbo. It is of course more powerful, but the acceleration seems smoother and has a very nice exhaust note. The interior is more refined as well. Go with the 12 or 13 when you're ready.
I also looked at/drove some of those cars. That Jag is a sexy beast!! Almost bought one, but the backseat is completely useless and I occasionally have my daughters (6&8) in the back. The Jag is also super light and I have gotten used to the feel of BMW over the last 2 decades--I couldn't make myself switch to the Jag. I must say though, the looks almost sold me!
2013 650i Orion Silver/Cinamon Brown