Well most people seem to like Malossi, i have never really heard anything bad about any Malossi parts ever. They are more expensive bit i think you tend to get what you pay for, at least you do if you go mega-cheap chinese.
Any brand name springs should be good tho, Pollini, Malossi, Nakura, Stage 6, etc, etc. I cant even remember what brand is in mine right now, Pollini i think
I bought some that came in a set of 3 for both Torque and clutch, got 1000, 1500 & 2000rpm's of each in each set and if i remember they were not that expensive, only a few quid dearer than cheap ass no name Scooter Assassins ones.
Do NOT buy clutch springs from Scooter Assassins, imo, i once did when i was a total noob and soon saw why they were so cheap. It was because they were total sh**. I emailed them to complain and asked how they could describe them as springs when they didnt spring, when i went to fit them they stretched out and clipped on then did not spring back! They gave me no refund and said i had fitted them wrong
I havent been back to them since. Funny how every other spring i ever fitted the exact same method worked fine