Volvo stopped making them, period! '04 was its final year (basically a '98 car that they kept alive too long) and I too have worked in Volvo dealerships for many years. There is NO convertable now made by Volvo. The upcoming retractable hardtop is suppose to come out by next spring but that's rumor and knowing Volvo, is likely to be later than that due to problems.
No Volvo tech wants to work on C70 convertables when it comes to conv. top problems or window regulators, both fairly common.

The vibration is termed "cowl shake" and is a known, uncurable problem with ALL FWD convertables by design due to lack of the roof structure. Volvo tryed to add more structural strength to its windshield area to compensate for that issue BUT they were unable to eliminate the problem completely. Volvo knew of this problem before the car was originally made in '98. You could have driven a then new C70 (right off a delivery truck) and you'ld notice the front suspension, steering wheel shaking compared to any other S/V70. To me and for a car that then sold for $50K, that'd be unacceptable and I'd never own one for that reason in itself, besides the fact that I hate all convertables.
Then Volvo used 17" wheels with Perelli low profile tires which often flat spot easily when the car sits for months (always happened at dealerships as they didn't sell well). Don't ever get close to a pothole with those tires or the wheels are bent in a heartbeat.