ok, let me share with you about my experience.
My latio is also less than 2 month old. I found the original suspension too soft too. If you read one of the thread on Coilover GB, you will find my big complaint there! The Latio back seats with 3 passengers (total weight less than 150kg), the tail pipe can hit the ground when went over the car park hump.
Anyway, cut the story short. So eventually, I complaint to TCS and it was kind of them to admit that the Singapore Latio suspension is comfort oriented. They scheduled a time slot for me to change my latio rear spring to Japan version, which is alot stiffer. The reason given by TCS was Japan road is alot better and flat compared with Singapore road which is bumpy (better tell LTA to buck up

)
After the upgrade, the ride was alot firmer and handling also improved. Personally, I like it alot better. Today, I just installed the front strut bar and rear anti roll bar to further enhance the road holding, now the car can take sharp corner very well and the ride is alot more steady that you will not feel the car rocking during high speed (I was on Lornie road this evening, going at 110km at some stage, and taking the winding/under construction Farrer road around 80km without problem). The steering response is sharper with the bars installed and also eliminate most of the body roll.
All this is achieved without lower the car suspension, original shocks and Japan spec rear springs, stock 15' rim and tires. I am very satisfied.
For those new latio owners, I learnt TCS has limited stock of Jap spec springs. So you might want to do it quickly, not sure they will bring in more when the stock finished. TCS will change the rear springs FOC if you complaint the ride is too soft to your liking and your latio can not even take 3 passengers at the back!
Good luck!