I've had my amp for about 2 months now and I'm loving it.  I've been wondering about a probably strange speaker set-up and want to see what you all think.

I've got 2 pairs of speakers in my garage where I do most of my hanging out (the amp's here too).  Both pairs (4 total) are in-wall.  Right now I'm running the smaller of the pairs and it really sounds great to me.  But...

How would it be to attach both pairs, 4 speakers total?  Each pair is 8ohms and I'm pretty sure the way to wire them is so I get a total 4ohm load.  Does that seem right?

I'd also like to make the speaker setup so I can "fade" between the 2 pairs.  I've got left to right balance control from my computer and think I need to make a control somewhere inline with the speaker cables.  Does that make sense?

As long as I'm not risking hurting anything I at least want to try this.  Should this be safe for my amp and speakers?  IF so, I would be eternally grateful if someone could post a diagram for me.  I'd offer my firstborn but that's not gonna happen at this point so that's out.