Hi Jose Luis,
You might get going on your Go 165 (165 liters x 262 long x 90 cm wide) with a 10.0 m2 Sailworks Retro (rigged for low end power) in 8-9 knots of wind, but you are going to have to work very hard to
get planing/stay planing.
The 10.0 m2 Retro is a very good sail for what you want to achieve, but a wider board (F-Type....Formula... or UltraSonic would "seal the deal".
I do not know about the JP Super Light so I cannot really comment. At 90 cm wide, I woulod be suprised if the JP SL gave you significantly better early planing that your '04 Go 165.
What size fin are you using?
Do you sail in shallow water or where there are weeds?
A big fin (66-70 cm) can really help to get you planing early, and when the wind gets up over 12 knots you can switch to a smaller shorter fin for better control.
Hope this helps,