Lilguy,
You might look at the Verny-Carron doubles . I do not have any personal experience with them (I do own Chapuis and Heym), but I have read lots of positive reviews on them . I also looked at them at SCI last year. They are top notch guns !!! They make an O/U in a 450/400 3" for around $7000.00 .
You can reload for all the doubles and do it a lot cheaper than buying the factory ammo. Just a matter of finding a load that will regulate in your gun.
Robert