Mike,
I haven't used the DGM Optics NPB filter, but I know Phil was very very impressed with it. He said it was the best overall deep sky filter he had used.
http://users.erols.com/dgmoptics/temp.htm
For those interested in following it up, the cost landed in Australia will be well under $AUS 100 as these are currently on special for $US55. I may be interested in ordering the 2" version so we could pool the postage costs there. Anyone else on the Central Coast interested in ordering one ?
CS-John B