So I post about this amp a lot, my buddy's Ampeg SS-140c. We took it into our local music shop and had the owner, who is very respected and knowledgeable in Boise, and he educated us a bit on how the Ampeg functions. Since it is a stereo amp it requires two cabs to run properly, as clearly demonstrated when he plugged the amp into two seperate cabs and the sound improved dramatically, the chorus became apparent and usable when it had previously been otherwise, the clean tone became fatter. It feels like the gain suffered a bit, but I think it just wasn't dialed in properly.

So my guitar player has been running this amp solely through an unnamed 4x12, which can handle the power put out, but it is a mono cab. We plugged in my Epiphone Valve Junior Extension cab, and the sounds came back. However I am concerned as the amp runs at 70 Watts per amp @ 8 ohms. The cab can handle 70 watt at 16 ohms. I forget about ohm-ages, so I am curious as to whether or not this will blow the cab or the amp.

1) Is the Epi okay to have the Ampeg go through it?

2) When Ampeg lists its output at 70 watts per amp @ 8 ohms, does it mean that I need one 8 ohm cab per amp which can handle 70 watts, or do I need two 16 ohm cabs that run at a total of 140 watts?

3) I know a few manufacturers have cabs that have a mono/stereo function, such as the Marshall 1960 AV or B-52 AT-4x12. If I got just one of these amps could I plug both outputs of the Ampeg into the one cab?

We can't really have walls of cabs up at shows, so we're looking into more space efficient options. Such as 2 Epi Valve Jr cabs (provided I'm not off about the ohm-age issue with that), or 2 2x12's, or if absolutely necessary one stereo 4x12.
Gear:1991 Fender MIJ Jazz/Squier VM Fretless Jazz -> Pitchblack -> Way Huge Green Rhino -> Boss OC-2 -> Boss DD-7 -> Markbass Tube 800 -> SWR 4x12.

Flat wounds. Flat wounds on everything. Everything is a little fatter when it's flatter.
My mesa boogie 2x12 has 2 input jacks that I use for stereo with my jsx, although I'm not entirely sure how one speaker is differnet than the other.