Nope. They share the same channel. Hmm, I'm looking at the Triple XXX as well. As far as clean tone goes its better than 5150.
But personally, getting the 5150 head might be unwise if you're living in an apartment. You can't crank the tubes at all. Even if you get an attenuator, it might still be too loud. 5150 head + 4 x 12 + attenuator can easily exceed 2.5k I think.
regarding the 5150 combo , it does decent cleans... but ofcourse its clean channel is nothing compared to a "cleaner" amp. Its dirty sound makes up for everything else.
it has shared EQ between channels but the lead channel is voiced abit differently so be prepared for a treble boost in the lead channel. very van halen sounding. But can be tweaked to mimic most distortions... ALOT ALOT of gain ... and very very loud.
if you dare... you can buy the combo. cut it in half.. convert into 60 watt 5150 head and 2x12 cab.