Since this thread is about alternative external speakers, I though I would point out something that some may or may not know about...
I went to a place that sells old computer parts around here - it's called "Weird Stuff Electronics". But any garage sale can be a great place to find them - as no one wants/uses this speaker setup anymore. These things are often thrown out in favor of the powered stereo speakers that are now available for computers.
If you can find an old pair of high-end 2-way UNPOWERED stereo speakers for a computer, you will find that they work MUCH BETTER than most external speakers that one can purchase specified for radios. They even have the right kind of plug on them as well - just plug it in. Since they are sold in pairs, you now have two of 'em; I use one for my base station and another in my mobile. I'm going to go back and buy another pair to use on my Ham rig and my 2m/70cm radio. The cost? A whopping $4!!! Prices may vary; but they are very cheap because no one wants them anymore. You very well may already have some or someone you know wants to throw them away!
More for us...
I was repairing a Cobra 2000 for a neighbor of mine a few weeks ago. I tested the Cobra extension speaker that comes with the Cobra 2000 against these 'other' speakers. Talk about 'no contest' - the computer 2-ways speakers made the Cobra speaker sound AWFUL by comparison. You will hear more natural-sounding receive audio - and the 'hash' that you hear will be less and not nearly as nasty-sounding.
Truth!
Will powered speakers work? Yes and no. The external speaker output on any radio is too 'hot' and needs to be stepped down if you are thinking about using the powered variety. Find a pair of non-powered Sony, Polk, JBL, Altec, Yamaha - and be ready for a pleasant and inexpensive treat. You would also be recycling them - in a sense. Bottom line? You will be VERY pleased. That is - if you are half as pleased as I am after this cool find. Just thought I would share this bit...