I have the same vehicle - 2005 Dodge Magnum R/T and I LOVE it!!! We purchased ours used - which there were some problems because the person who owned it before us did not take care of it mechanically. That being said, I would not trade that car for anything. This is my daily driver and I love to drive it! Ours is basically fully loaded (navigation system, moonroof, power everything, 6-disc changer, etc). We have had some minor electrical issues, which I think is due to a remote starter being improperly installed - the back driver-side window won't go down, moonroof will open back up if you are putting up the windows at the same time. We will be getting these issues fixed at a later date sue to child #2 being due next month and I am laid-off. The rear shoes (brakes) were bad, but again, we and our mechanic think it is from lack of maintenance.
All that being said, my husband and I LOVE the ride - very smooth and comfortable. Great storage in back, but it is less than the Chrysler Pacifica we had previously due to the "chopped" roof line. I also love, love, love my navigation system! It can fit 2 booster seats in back, but I don't know if it can fit those along with a child seat. See if you can find one in the area that is for sale and bring the 3 seats with to test out. It also geats pretty good gas mileage too - surprising for a HEMI, but the design of the car helps the aerodynamics as well as the ability for the engine to switch to only 4 or 6 cylinders while driving on the highway and then kick the extra cylinders in when needed for passing...or just to go fast! It is a FAST car, which I absolutely love. I can't say enough about it. My husband is trying to talk me into getting a new car because of the little problems we have had with it - he is worried something BIG will happen, but I wouldn't trade it for anything. Also, when looking for one, see if you can find one that has only had 1 owner - for $150 you can transfer for 7 year 70,000 powertrain warranty! We needed a gasket replaced shortly after we bought ours and only had to pay the deductible!