A second the B22 as a good amp for the B22. I picked up my pair off of ebay for $50ish bucks. Did the mods myself for another $10. So they can be had inexpensively if you are patient.
On a side note I have yet to install the fabric over drivers, so my ears touch the electret. Needless to say if I touch anything grounded I get a nice little shock through my ears. So if you get them and mod them make sure you install the fabric over the drivers.