Depends on the year...
6x9's
dodge factory speaker sizes are 6"x9"
Yes Dodge Chargers are used as rental cars. Cars of all sizes are available.
18
Tire sizes for the dodge charger may vary depending on if it is all season or high performance. All season tires are 245/45R20, and high performance are 255/45R20.
25mm
318
the 225 cu in slant six, the 318 and 360 v8's
As of 2009 there are three V8's in production. The 4.7L, and the 5.7L and 6.1L Hemis
They come in all sizes and weights. About 5 pounds is average for a 10 amp charger.
Dodge charger tire sizes can vary. If you have the all-season tire option, then the size is typically 245/45R20 on all four wheels. If you select the summer tire/high performance option, then the rear tires are 255/45R20. Either way, the rims are 20x9inch. There are a number of owners using a wide variety of tire sizes - 275/40R20 are common wider rear tire sizes and work on the 9 inch stock wheels. You can find other options by browsing the discussion forums of SRT8 owner's clubs online.