The current 9-3 is based on the 900 which debuted back in 1993. It offers no rollover protection (just a high deck and headrests that limit visibility), has a dated dash, and sloppy handling. The body structure is incredibly weak and there is plenty of cowl shake when going over bumps. The new 9-3 is coming out next year...thus the 0% financing.
The Volvo C70 has a reinforced S70 platform, which is the same as the 850 that also came out in 1993. It's structurally more rigid than the 9-3 and offers roll-over protection, but it still feels like a wet-noodle when compared to the 3-series. 2003 is also the last year of the C70 = no resale value.
The more solid buy would be the 3-series. It's overpriced and underpowered (in the 325CiCa form), but you'll sell the car for much more in the future. It's leap years ahead in safety, handling, and overall performance.
The new A4 Cabrio is work looking at too. So is the New Beetle cabrio, that is, if you don't mind being seen in one. Both offer roll-over protection and advanced transmissions (CVT in the A4, 6-speed auto in Beetle.)