Hi John and welcome to Beoworld!
Have a look at the following compatibility table so you can work out compatibility between the various handsets and bases:
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Assuming that you are using a BeoLine US with your BeoCom 1s, you should already be able to connect up to 8 handsets. Perhaps you have other older/unused phones registered to the base, in which case you should delete them to release space for others.
If you do have the BeoLine US, then you should be able to connect a BeoCom 2 (US) with the type numbers listed above.
With regard to 'refurbishment' of your existing BeoComs, there is little that you can do other than fitting new batteries - this often solves problems with the phone or display and would be my approach in the first instance.
Ref speakerphone, I am not aware of any easy options, although some of the older 'cabled' BeoComs have built in speakerphone - BeoCom 2000 for instance. You'd have to be careful to get one compatible with the US phone network.
I hope this helps - come back and ask if you have further questions.