Well when you just look at the numbers.......2inch....1.7inch..it doesn't look like much....
But on a car, 2 inches is quite a difference. If your car is being lowered via lowering springs, I'd say it's ok. If the springs are stiffer in anyway, it'll be like kickin_81 said, decrease your shocks lifespan. We say this because on the street, you go through several ups and downs along with pot-holes. On a smooth race track or city roads that are smooth where you live, I'd say it's ok.
It's best to get stiff struts along with any lowering springs that are stifffer. If just progressive springs, I'd say it's ok, but that's just my opinion. Progressive springs are quite nice though for at least some comfort and performance in it.
2 inches, you'll see a huge differnece! It is a little much but it'll look just perfect! Just know to choose your tire sizes.
FuJi