Yes just the miniplug-to-2RCA if they are less than 3 feet apart, if farther away you need the adapter and longer RCA/RCA patch cale too (all 3 parts). For a VCR or cable both you just need the RCA/RCA patch cable.
From the description of the Kenwood at buy.com it does not have a 5.1 analog input, just stereo analog inputs, so you only need one set of cables from the PC to the receiver.
If you want surround sound for games, you would need to pick a different home theater package that includes a receiver with analog 5.1 input. The Onkyo ones mighr (I haven't checked) or you could buy separate speakers, receiver, and DVD player.
(Remember, even if you buy a soundcard for the PC, a digital connection will only give you 5.1 for DVDs not games)