Extension cab for Ampeg BA500?

[mfbolton]

I'm looking to get an extension cab for my Ampeg BA500. It is a 4 ohm rig as it sits, and can handle down to 2 ohm. I would like to stay with an Ampeg cab, but they are a bit hard to come by in a 4 ohm rating. If I use an 8 ohm cab, the overall ohm rating would be 2.7. What are the downsides of mixing different ohm ratings? I've found a good deal locally on an Ampeg 8 ohm 4x10 cab, but if it is not going to sound good or be damaging to the amp or speakers, I'll keep searching.

Thanks and Happy New Year!

[UncleWally]

I got a PF-500 with a SWR410 at 8 ohms. I bought a ext cab Hartke 2200 PRO that is 4 omhs. I want to use them both at the same time. No clue here.

[RickenBoogie]

mfbolton- you want to find a 4 ohm 2x10. Ampeg made a few models, including the BXT210M. But ANY 4 ohm 210 will work. I used a 4 ohm 1x18 with that amp, a 4 ohm 1x15 would work as well, but a 210 would be ideal.
unclewalley- you CANNOT use that 4 ohm ext cab with your 8 ohm cab, as your amp is 4 ohms minimum. You can use ONE 4 ohm cab, or TWO 8 ohm cabs. It's best for them to be identical, in any case.