Hi MLSpeed
1) Early Prince had hods of problems. I think you already know about this. This Prince carries 8 mods which has made this engine very reliable. The 8 mods address reliability issues. Look at page 1,all the mods are listed. I've had my car for 18months,not a single engine problem. There are about a 100 owners here in the forum,no one has complaint about the engine.
2) Both 4spd and 6spd are reliable. 6spd is silky smooth.
3) 2litter NA is the reliable 407 engine,but given a slight uplift with 8hp more.
4) NAZA's support and service has been less than adequate. Improvements are being made,but there always room for more.

Both NA and 1.6t are worth every cent. With year end sales the NA is 95K,imagine getting a conti at this price,it's a steal!

The 1.6t is best bet for money. There is nothing to match this car at this price with this spec! $17k extra for this car is really cheap.  The 6spd gearbox alone cost cost more than $17K! Look at the extras you are getting. My wild guess, it may cost $70K to add on all the extras after market!