I assume you have 205/55R16 size tires on your C70. For the softest possible ride on your car you should check into the new Goodyear Comfortred tires. They are highly rated at tirerack.com and I have a set on my 1995 850 and they give a noticably improved (softer) ride over other tires I have had. These tires are "H" speed rated which is one level lower than the "V" tires that probably came on your car. However, since you don't drive aggressively, the "H" speed rated tire is more than adequate for your needs. Good treadwear also - rated for 80,000 miles. They also have a 30 day trial period and will let you exchange them for a different tire if you don't like them. I am confident you will be pleased!