I'd keep an eye on the forums - nasioc and iwsti - for a set of STI or '09+ springs. The fit will be perfect and you'll most likely find them for dirt cheap, especially compared to some aftermarket setups. Heck, you may even find a full strut assembly for cheap, which includes the strut, spring and top hat, so all you'll have to do is unbolt the old strut assemblies (and endlinks if there's interference,) remove, and bolt in the new strut assemblies.
An added benefit of staying stock is also that the dealer will most likely not know should you blow a strut and require warranty work. I don't believe the damper was changed from '08 to '09, just the springs and sways.
I just gave away for free my stock springs and sways to an '08 2.5i owner. I didn't want to deal with selling or shipping, so I posted a first-come-first-served thread and it was gone within a month. I thought they'd be gone faster, actually, considering they were FREE!
Anyway, I recommend against lowering springs, unless you're doing it purely for looks. You'll lose travel and may end up riding on the bump stops through heavy cornering loads on bumpy roads, which will be worse than softer springs.
I have Racecomp Engineering Regular Guy springs on my STI, and they only lower 5mm (1/5") Going with too stiff of springs will give you a similar effect as blow struts, though, albeit to a much lesser extent, since you'll be oversprung (or underdampened.) In this case, your spring forces will not be matched properly to your stock dampers, which will make things much bouncier.
Going with too big of sways on the mushy '08 springs will also have consequences. Sways work by trying to compress the opposite-side spring to maintain the loaded side more level. In other words, if you're making a sharp right turn, the left wheel will be the one that compresses. The sway bar will transfer some of that load (based on the torsional/bending rigidity of the sway bar - how much it resists twisting and bending) to the opposite side. The result for a too-big sway bar and puny little springs is that heavy cornering loads (or even something as simple as coming into your driveway at an angle) will still compress your loaded side, but transfer more load to the unloaded side than it can handle, causing it to compress that spring and lift the unloaded tire off the ground.
While having some stiffness for transferring traction to the loaded side is good, having your wheel lift off the ground during a heavy turn never is. For daily driving, however, you'll never notice this, and sway bars alone may be sufficient.