I am bigger and heavier than you, I bought a Ti (maidened it today actually) because I didn't like taking an AI so close to its design capacity limits (plus I like the capability to take others out with me)
In addition, at 6'3", with a big ar$e, there was insufficient legroom for me to comfortably operate the Miragedrive, so I fitted a skipper seat up 6 inches and back about 3 (4 without the swivel mechanism)
Now, with the Miragedrive setting of 7 (pedals as far forward as possible), my leg moves to almost full stretch which is very comfortable pedalling.
So I would definitely recommend you extend your budget to buy a Ti instead. You won't regret it!
2012 Tandem Island "SIC EM"www.scenefromabove.com.au