From the AMD site:
http://www.amd.com/us-en/Processors/ProductInformation/0,,30_118_9485_9487^10248,00.html
Code:
3700+ 2.4GHz 1MB 754-pin
3700+ 2.2GHz 1MB 939-pin
3500+ 2.2GHz 512KB 939-pin
3400+ 2.4GHz 512KB 754-pin
3200+ 2.0GHz 1MB 754-pin
3200+ 2.0GHz 512KB 939-pin
3000+ 2.0GHz 512KB 754-pin
3000+ 1.8GHz 512KB 939-pin
Depending on which a64 3000+ the clock speeds are infact different as you pointed out.
I can never keep the model number right anyways. As for dual channel or not if it's a 939 it's a dual channel chip but will only function as dual channel if you have two sticks of memory installed.
The numbers make a little more sence now:
2162/1800 is 20% faster Mhz wise but only 11.5% faster in sieve.
I've basically retired all of my other computers except for two a dual barton 512Kb each of them run at ~2.3Ghz on 133 fsb. And a 2.4Ghz at 200fsb.
Like Maddog said tough to retire those, especially the dual. I think I won't upgrade again until the socket M2 comes out.