Hi tavman,
Sounds like we're in a very similar boat. I recently purchased a Road King head and 4x12 cab. I only use my RP7 through my Marshall VS65R and that sounds focking awesome. I'm still working with the Road King...it's awesome, but I can't seem to harness Ch 4 yet.
I'm also looking for delay pedals. The Boss delay pedal seems to be quite popular. I wonder if it's really that good, or if it's just a popularity issue with the Boss brand name. Let me know how your search goes!
By the way, the RP7 sounds like absolute garbage with the Road King. It only sounds good with very high quality effects, and my RP7 is 7 years old and definately not high quality anymore (if it ever was).