I had an ST170, and like was said above, the gearbox was the worst part of the whole car (so much so, I decided to sell it and order an ST which I get on the 1st March). Far to clunky and about as long as a broom handle

. If the ST revs at 3400 ish @ 70 then don't worry too much, the ST170 didnt' rev a great deal lower in 6th.
/edit oh, and I had a Skoda Octavia VRS and that had only had 5 gears, and it really didnt bother me that much. If anything the ST170 was annoying with 6 gears because you were out of first before you knew it - redlined far to quickly.