Wadda Ya want?
The bikes have fairly soft springs, so they ride pretty nice. The footpegs are low to provide a more comfortable riding position. The OEM suspension parts are cheap to keep overall costs down. The bike isn't a sport bike. To fine-tune the suspension you'll need fully adjustable dampers front and rear. The springs will also likely need to be changed. Just curious, but have you lubed the rear suspension links recently, and changed your fork oil in the last year or two? Of course, lowering links will drop ground clearance if you happen to have/use those. I'm guessing you can make it handle better in the twisties with more ground clearance, stiffer springs, and stiffer damping, and a fork brace, but that flexy frame is going to limit ultimate performance. Or you can make it ride nicer with the soft springs, less preload, and perhaps a little less compression damping. Doubt you'll get both. Or you can trade it in for a $20K BMW which electronically senses and changes these parameters on the fly. You get what you pay for. Be advised that suspension changes and adjustments are not for the inexperienced. You could spend a pile of money on new parts, and without the correct adjustments, make little positive improvement.