We discovered QC Terme several years ago - and we've stayed there 4 times already (and are booking it for the coming year as well). We've recommended it to many friends and everyone agrees that it's a great place to stay. Here's why -
If you're going to fly to the FCO Rome airport and then face renting a car and driving while you're exhausted and jet lagged, you might want to consider arriving a day or two early to start your trip with a night or two at QC. Get over your jet lag at a remarkable, relaxing, quiet, and pleasurable place! Then taxi 6 minutes to the car rental place and start your trip to your destinations in Italy.
And at the end of your trip, if you're going to fly out of the FCO Rome airport (and face the stress of waking up at the crack of dawn, checking out of wherever you are staying, driving to FCO, returning your car, and time-consuming luggage and security checks), we highly recommend staying at QC for a night or two. Every time we do this, it's fabulous.
QC is located so close to the airport, but you don't hear the planes. It's quiet. It's tranquil. (In fact, the first time we stayed at QC, the person showing us our beautiful room said that he hoped it wouldn't be too noisy. We were concerned and asked him about the noise. He told us there was a fountain outside!)
QC is elegant, but not "stuffy" or pretentious. Elegant formal grounds (kept beautifully green even if there's a drought elsewhere in Italy). Beautiful marble and stone floors. Thick towels and bathrobes. Great selection of toiletries. Superb breakfast selections. A late afternoon free buffet of drinks and food. An after dinner drink in the lounge area. All included in your room rental.
And a restaurant - with outdoor (and indoor) dining, good service, and white tablecloth dinners.
Now add in the super enjoyable heated pools (there are quite a few) with amazing jet streams that massage and relax you while you are surrounded by greenery and blooming while roses and lots of Italians.
And the option to book massages.
And a very fair price for your room or suite.
And you can do great day trips (to Villa D'Este, Hadrian's villa, Ostia Antica, the Subiaco monastery) if you're so inclined. A fine start to your Italy trip - and/or a fine end to your Italy trip!