It'll definitely be a change in regards to power. The IS 300 (217hp) has ample and more responsive power whereas the CT (134hp) is a bit slower but makes up in mpg's (43 city/ 40 hwy). Your IS 300 might have more space than the CT. You can fit five people in the CT but more comfortably in the IS 300.
I love my CT and purchased it back on March 2011 and have over 70,000 miles. It's a great daily driver and commuter car. Not only will you save on gas but also maintenance. The CT does have a nice sporty look to it.
If you can, keep the IS 300 and get the CT 200h.
Last edited by Trexus; 05-23-14 at 11:51 AM.