driving tour from tuscany to barcelona

Way too ambitious.
First of all you need to know that if you pick up a rental car in one country (Italy) and drop it off in another (Spain or France) the drop off fees range from 400 to 600 euro, so probably more than the entire rental charge. So keep that in mind.
In these cases it's best to drop the car off at a location within the country, near the border if possible, proceed by train to the next country and, if necessary, rent another car there.

But the other issue is time. 7-9 days are barely enough to see Tuscany and the Cinque Terre. For example Venice, should take about 3 nights (that's my recommended length of stay there). Tuscany will take another 3 just for the country side, but if you want to include Florence, then you need at least 5 in the region of Tuscany. The Cinque Terre, at the very least 2 nights. So there isn't much left of your vacation. Consider that driving to France (assuming you don't care to spend 500 euro in drop off fee) is a long way. From Florence to Montecarlo (which I used to drive a few times when I lived in Florence) was a 5 hr trip, with no stops and at a good speed. I've never driven to Barcelona from Florence (only flown, a few times) but some of my friends have. It's a 10 hour drive at very high speeds on the freeway with no stops except for gas.

I think with 7 to 9 days, you should limit yourself to Venice, Tuscany, Cinque Terre. Rental car is recommended for the Tuscany countryside and small villages, but totally unnecessary (actually a hassle to have) in Venice, Florence and Cinque Terre. Therefore pick up the car when you leave Venice. Go and do the Tuscan country side first. Then drop the car off in Florence. Stay in Florence without a car, then go to the Cinque Terre by train, where you won't need the car at all either.

Alternatively you can stay in the countryside of Tuscany iwth a car, but visit Florence from there (on day trips). Don't stay in a Florence hotel with a car. Then drive to La Spezia (near the Cinque Terre) return the car there and take a short train ride to the Cinque Terre. Then take a train to the airport where you depart from (Pisa is the closest, otherwise Milan or Rome, the largest, are only about 3-4 hours away by train.

Roberto has you on the right track. Tuscan towns are much more interesting when you walk around and explore them, not just drive past. Last fall, after my Italy tours and many other trips to Italy, I spent about 10 days to visit 10 small towns in Tuscany and Umbria, some for two-night stays and some for a half-day en-route to the next destination. Some people would do it more slowly, especially if including a larger town like Siena, which has a lot to see. The same issue applies for France, of course.

Cel,

Is this your first trip to Europe?

If I had 7-9 days & had not traveled to Italy before, I'd explore the big 3; Venice, Florence & Rome.

If you plan to visit all the destinations you mentioned in your post, you will end up driving most of the time just trying to get to your destination.
You are not giving yourself enough time to enjoy any particular location especially when you plan to spend one night at many of your destinations.

Keep in mind that if you rent a car in Italy & return it in a different country ( France or Spain), it will be extremely expensive.

Check this website to give you an idea of travel time between your planned destinations:http://www.rome2rio.com

If you want to visit Venice & Tuscany, you may want to fly into Venice then take a high speed train to Florence.
You can then rent a car in Florence & drive to Assisi (Umbria) & hill towns in Tuscany.

cel,

I most definitely agree with Roberto - your proposed Itinerary is WAY too ambitious for the time frame you have (not too mention the steep drop-off charges for the rental car). Hopefully you're not relying on Mapquest or whatever to estimate driving times, as I find those usually underestimate the time (sometimes significantly).