Originally Posted by Vince Klortho
It will need to be 8 ohms and it will get a maximum of 250W. That's the max though. It will not get that all the time so you could probably get by with a 200W speaker if you wanted to as long as don't play at max volume all the time. If you get a Hartke 15 cabinet it will be able to handle at least 300W, depending on the model. Some of them handle 500W.
Cab would be 8 ohms and you'd get 250 watts per cabinet, but I would make sure the 15 is rated at least at 300 watts so you could use it stand-alone.
Also the point about mixing disparate cabinets is a good one, speaker cabinets do not have an inherent sound based on the size of the drivers in them. Many 410's go lower than many 115s. Check out the efficiency of each cabinet to try and get some handle on their relative loudness, most 410s just bury 115s in terms of efficiency, which ends up leaving your 115 making very little overall contribution to your sound/volume. I agree, check the stickies for more in depth information.