I have a rockford fosgate 600w 5 channel..its bridged to two focal 70watt 4 ohm speakers. and it has a dedicated sub channel that is connected to a pioneer 4 ohm 200w 10" sub.
The rockford is rated to deliver 150w x 2 bridged at a 4 ohm minimum each and its sub channel puts out 200w rms.
Its brand new so should it be getting really hot? All the gains are a little past halfway.
Link to Amp: http://www.rockfordfosgate.com/products/product_details.aspx?itemid=118749
It's not uncommon. a multi-channel amp is typically class A/B for the full range channels, and class D for the sub. Class D amps run slightly warm usually, as they are very efficient (80+%) but class AB amps run pretty hot, since they are less efficient at around 65%, the rest of which is usually lost to heat. I use some older Orion amps that run so hot, even at lower volumes, that you can't touch them once they warm up without burning yourself.