Blimey, that's a big area to come up with 5 or 6 sites!!

I'm only familiar with West Penwith really (and getting to know Dartmoor by inches). If you get as far as West Penwith, you can easily see a load of sites in one day. My recommend would be Tregeseal and Nine Maidens/Boskednan stone circles, both of which have other stuff near by, e.g. Kenidjack Common holed stones, Ballowall Barrow, Boswens Menhir, Watch Croft cairns and stone, Men Scryfa, Men-anTol (if you like other people at your sites).

Carn Euny is a great Iron Age settlement with (restored) fogou, Chysauster is better preserved but likely to be busier and the fogou is gated off. The "quoits" at Zennor, Mulfra and Chun are all excellent (Lanyon is a bit mobbed and close to the road for my taste). Boscawen-Un and Merry Maidens circles are excellent as well, I prefer the two circles mentioned above as they're on open moor, but you could get to all four in a good day. I know you like a nice hillfort, Chun and Trencrom are both excellent.

For Dartmoor, favourites would include White Moor stone circle, Down Tor/Hingston Down cairn circle and row, Yellowmead, Brisworthy stone circle, the amazing complex of rows, cairns and settlement at Drizzlecombe. Kiss in the Ring/The Dancers stone row/terminal circle is terrific, but quite remote.