handling - tires?

I have a 2001 LeSabre Limited with Grand Touring Suspension. It rides on Firestone Affinity 16" tires. I'm not satisfied with the way the car handles or feels. Centering is touchy and vague which require constant corrections. It makes me feel like I'm fighting to keep it on a straight line. I've had it to the alignment shops and they say all is within specs. The one thing I noticed was after a tire rotation, it seems to handle better for a while. This leads me to think a change of tires will go a long way to correct the problem. Is this just a characteristic of the car or has anybody had this problem and solved it. I've been looking at Bridgestone Turanza and Michelin tires. I hope somebody can help shed some light. Thanks, Alan

It sounds like the tires. I have Michelen X-Ones on my car. Always given me great handling, and i have never hydroplaned (aquaplaned) with them. Thyey are a bit pricey (around $450-500 for a full set), but they are worth it to me.

Thanks for your reply. I've changed the tires to Bridgestone Turanza
LS-Hs. The car seems to handle better now and the ride is great!