How about purchasing an external Behringer pro amp, they are very popular around here, although the larger ones are much more powerful than what you need..
Like Behringer Europower 1500, don't think they are more expensive than the plate amp's you need....? well, I really don't know this, well.... and it may power a seond UFW-10 if you should be so lucky as to get one more sub later.
EDIT: Oh well, the plate amps are cheaper, but I guess the Behringer easily outperform them......
http://www.behringer.com/EN/Products/EP1500.aspx
This is $439, but it's stereo amp that may be bridged
Plz tell us how you go, will be very interesting to hear more.....