George,
I've just added Duncs mod to my 598 DP into a DVDO HD+ scaler, the picture has been improved no end. I still have the analogue prog. scan component connected and switch back and forth between them, no comparison!
Go for the mod, you won't regret it.
Now that I am so impressed with the gain I'm now sorry that the DVDO machines only allow 1 SDI input (including the VP 30) therefor I won't be able to get a sat. box modded with another SDI output.
That said, I'm happy with the quality of the picture outcome from it (RGBs from my digi box for TV).
Ian T.

598DP SDI, 568.25MM, Crystalio II 3800, 435 XDE (soon to be 50pf20?), NVA A80 x 8, AE2's, AE2 Pro, AE1's.