Suspension advice - again!

I know suspension questions pop up regulary, but haven't really found an answer to this one.

Iv got a 650 sport, with stock suspension. I have thought about changing front springs, but haven't worked out (1) whether worth it and (2) what spring to go for.

I am pretty light (9 half stone), so Iv read the stock prob isn't too bad for me, but a good half of the time I am 2 up (with girlfriend who weighs about 12 stone). If I get springs for my weight, will it be far too soft 2 up, and if I get springs for combined weight will it be too hard when it's just me on the bike??

Help!!

Personally I would just change the fork oil using 10w and ensure the rear shocks still damping well if not a Hagon would do me.
Also remember to up the rear pre-load one click when 2 up.