input and rca connections on amp

My question is specifically to weither or not my following connections will cause DAMAGE to the amp.

IT's a 4 channel inifnity 7540a.   I have the front channels on the amp connected to my head unit via the speaker level inputs.  I have the rear channels on the amp connected to my head unit via the rca inputs.  Currently the amps is driving my front component speakers and rear coax speakers.

I understand that the rca will produce cleaner sound than the speaker level inputs, but I only have one set of outputs on the head unit.  So I hooked it up this way.    The gains were set indepentanly on the front and rear channels.  I didn't want to use a y connect on the rca because I use the fader controls on the head unit.

What's the word? safe for the amp or not?

Thanks

Some amps have a maximum level of input on the high level input, so if you are worried about this, just use the y -adapter, a lot less painful than a blown amp. You might want to contact Infinity for this one though.

Why though, are you using the RCA for the rears and not the fronts? The front speakers are generally more important.

I'm only using the rca for the rear because I only have one set of rca outputs on the head unit.   This setup is actually temporary.  I have two subs sitting in boxes waiting for me to build a box.  I just want to make sure the using the differnent inputs will not harm the amp.  As far as the power limit, the head unit only puts out 20 watts rms.   It's pretty low.  I see about contacting infinity for the specifics then.  I was just curious if this was a generall no-no.

When the box is built I will move the fronts over to the rca and drive the subs with the rear channels bridged.  I'll then use the summed output rca on the amp to move the signal over to an older 50W rms amp to drive the rear speakers in the cabin.  I have questions about the subs, but i'll put that in another thread.