The lower photo resembles one I have from them. Don't know for sure but it most resembles B. 'Silver Cloud'.

I don't know the names - so many varieties out there today that it is becoming almost impossible to keep up with them all. Contact Exotic Angel and ask them what the name is and why don't they label them (I think the answer will be they have a billion tags already printed and will use those before doing any new tags). I looked on their website and saw that none of their photos matched what you have. The red one reminds me of Omaha Beefsteak but I haven't seen that name for years. Another possibility is Red Robin 1 or 2. At least one of those may be a parent to your plant. Check out Antoon Hoefnagels' begonias as well (from Holland I think) - Red Kiss is a better match. And if that is the case maybe your silver is Silver Limbo.

As for care you might try Brad Thompson's Begonia World for starters. Rexes can be a bit fussy - in winter - susceptible to mildew attack and also will probably go semi-dormant. Treat for mildew when you see it "bloom". Do not despair if your plants start going downhill either - they are probably stressed from going from a bright greenhouse to a home environment. Do not keep the soil soggy wet but do not let them go bone dry either (easier said than done). The main thing is to keep the rhizomes (stems) healthy and plump - they will eventually put out new foliage when the season and conditions are right.

http://www.bradsbegoniaworld.com/

http://www.costafarms.com/plants/rex-begonia

http://www.kwekerijhoefnagels.nl/info.html

I've also been looking for the name of the silver-leafed rex you have pictured (mine was also labeled the same way when I bought it). Compare it to B. 'Silver Limbo'. I haven't been able to find much info about it, just a few pictures via Google image search...please let me know if you have/had more luck!