let's start with this.....your T2 amp has 2 speaker output jacks in the back which are identical to each other. the amp's operating impedance is self-adjusting, so you can use a 4ohm, 8ohm, or 16ohm cab and the amp will automatically run at the detected impedance of the cab. i believe the T2/V2 heads do not output in stereo, only mono. so each "speaker out" jack runs in mono. when your picking your cab, only pay attention to the mono specs. some cabs have a swith for mono or stereo so be sure you are running it in mono.
now, your amp will run at the following power ratings into a mono cabinet:
480w @ 2ohms (wouldn't recommend this option, amp gets real hot)
400w @ 4ohms
280w @ 8ohms
160w @ 16ohms
the cab you choose must be able to handle the indicated wattage at the indicated impedance listed above. for example, if you find a cab that is 200w max @ 4ohms, it won't work cuz your amp will be putting out 400w @ 4ohms.
to answer your question about running two cabs for a full stack....gets a little more tricky now. cuz you can run each speaker wire from the head to the cabs directly, or you can run one speaker wire to the first cab, then if the cab has a "parallel out" jack, you can just run another wire from the first cab to the second cab, but the impedance will be cut in have, so again, it gets tricky. find a cab that can handle the watts/ohms you wish to run and just buy two of them. here are some example options:
2-4x12 cabs, at least 400w handling capacity @ 4ohms mono
2-4x12 cabs, at least 280w handling capacity @ 8ohms mono
2-4x12 cabs, at least 160w handling capacity @ 16ohms mono
here's my two cents.....buy a randall RS412XL100 cab, run it at 4ohms 400W, and you won't need a second cab!!!! THAT WILL BE LOUD!!!