Many 2.5 V6 156 2002 interior face lift models and beyond are Q-system's
The manual 6 speed is quite rare in comparison.
Don't let the Q-system put you off, it is certainly worth considering...
Owning one myself and also having a manual v6 in the family, I can honestly say there isn't much difference in performance in the real world in fact if anything the Q-system makes better use of it's gearing at overtaking speeds, alarmingly so. It does however take some practice to get the best out of the Aisin box (not a slush box ZF found in the 166) as it can bog down on initial take off from the lights and junctions...
It soon makes up for it shortfall though once the tall gears have you wafting past at 75mph+ in second gear alone, while a manual V6 owner is fumbling midway between third and fourth
It is far more civilized in traffic and cruising than the manual yet once you hit the sport button or slip the rifle bolt-like gear lever into the 4 speed H pattern, then it turns into a beast on demand... Then there is the torque converter and what it gives... No need for a Q2 diff as you can pull out of junctions , sweeping bends and corners without the hint of drama as it grips reassuringly as you have the V6 torque pull exactly as and when you need it, no waiting to put the power down.
Then there is the reliability of the box itself... Bullet proof and a lot can be learned by Fiat/Alfa on mating a the same mechanical's and electronics in the Aisin Q box that has been proven to handle 400 bhp+ in Toyota Supra turbo's and Lexus V8's,
Unlike self detonating Lsd's and clutches and DMF flywheels made of jelly in many of the manual models.
Ice mode is also pretty trick and works surprisingly well on even 6" plus snow covered, untreated roads.
Fuel economy is never going to get above 23mpg around the town but only say 2mpg less than a manual.
The initial bog down on take off at maximum right pedal usage.
Only 4 forward gears, yet there is only one other car that I know of that can achieve 0-145mph in one gear if you so wish and that cost £100,000 and made by Aston Martin
Some party trick
Everything else that the 6 speed manual should have been.
Would I swap my Q-system for a 6 speed manual?
Having regular use of both...... Nope, I love it!
Like I said, worth considering