You don't need to "match" the amp and cab, any cab that's 4 or 8 ohm and can handle 200 watts or more will work. If you're going to be playing on stage in a band, I'd really recommend a 4x10 cabinet. A 1x15 or 2x10 cab will be fine too, it just depends on how much volume and bass you need. Used cabs can be a good value, but be sure and play through them before purchasing.
Don't forget to use a SPEAKER CABLE to connect the amp's output to your (future) speaker cabinet, avoid the temptation of using a guitar/instrument cable, the wires are too thin.
I used to own one of these (basis of my username), and I loved it. I played it through a G-K 4x10 neo cabinet. I ended up trading it in on an Ampeg pf-500.