You might try having the radiator flushed by a radiator shop, if you have
no leaks in it.  Most shops will charge $30 to flush and they can then tell
you if is flowing well.  My van's previous owner had introduced stop leak
into the system and basically clogged the radiator.  I priced radiators as
well and just before ordering the thing I drove it by the radiator shop,
sure enough clogged with very little flow, 15 minutes later the thing
flowed well.  A huge savings and well worth the effort since they told me
they wouldn't charge anything if it didn't flow afterwards.
Good luck!

Jeff Birk
'89 Wolfsburg GL (Road Whale)
'82 MB 240D (Slo Mo)